VB.NET - Error Handling in Generic Class for PDF Merge

I've modified the "master" method to incorporate the suggestions provided by @Heslacher. I had been concerned about the fact that the overloaded methods didn't have their own Try...Catch blocks around the calls to the "master" method, but after testing with and without them, I now understand that, as long as the original calling method has it, any exceptions will "bubble-up " through the overloads as expected/intended.

Additionally, by testing the exception handling, I found a couple of places in my original code where I was incorrectly passing a "default" value into the "master" method instead of using the value provided by the overload. I've corrected these occurrences, and everything should be "cleaned up". In the spirit of sharing, here is the updated code:

''' <summary>
''' Class for manipulating PDF files
''' </summary>
Public Class PDFManipulator
#Region "PUBLIC PROPERTIES"
    Public Property Warnings As List(Of String)
    Public Property Errors As List(Of String)
#End Region

#Region "PDF MERGE METHODS"
    ''' <summary>
    ''' The file property to use for sorting the files before merging
    ''' </summary>
    Public Enum PDFMergeSortOrder
        Original
        FileDate
        FileName
        FileNameWithDirectory
    End Enum

#Region "PUBLIC METHODS"
#Region "CONSTRUCTOR"
    Public Sub New()
        Errors = New List(Of String)
        Warnings = New List(Of String)
    End Sub
#End Region

#Region "OVERLOAD METHODS"
    ''' <summary>
    ''' Merges multiple PDF files into a single PDF file
    ''' </summary>
    ''' <param name="PDFFilePath">The path in which to search for PDF files to merge</param>
    ''' <param name="OutputFileName">The PDF file to create from the merged PDF files</param>
    ''' <returns>A FileInfo object representing the merged PDF if successful. <cref>Nothing</cref> if unsuccessful.</returns>
    Public Overloads Function MergeAll(ByVal PDFFilePath As String, ByVal OutputFileName As String) As System.IO.FileInfo
        Return MergeAll(PDFFilePath, False, OutputFileName, False, PDFMergeSortOrder.Original, False)
    End Function

    ''' <summary>
    ''' Merges multiple PDF files into a single PDF file
    ''' </summary>
    ''' <param name="PDFFilePath">The path in which to search for PDF files to merge</param>
    ''' <param name="UseSmartMerge">Identifies whether to use a regular <see cref="iTextSharp.text.pdf.PdfCopy"/> or the <see cref="iTextSharp.text.pdf.PdfSmartCopy"/> for merging</param>
    ''' <param name="OutputFileName">The PDF file to create from the merged PDF files</param>
    ''' <returns>A FileInfo object representing the merged PDF if successful. <cref>Nothing</cref> if unsuccessful.</returns>
    ''' <remarks>Using the <see cref="iTextSharp.text.pdf.PdfCopy"/> (<paramref name="UseSmartMerge"/> = <c>False</c>) may result in larger files, 
    ''' while using the <see cref="iTextSharp.text.pdf.PdfSmartCopy"/> (<paramref name="UseSmartMerge"/> = <c>True</c>) may result in longer processing times.</remarks>
    Public Overloads Function MergeAll(ByVal PDFFilePath As String, ByVal UseSmartMerge As Boolean, ByVal OutputFileName As String) As System.IO.FileInfo
        Return MergeAll(PDFFilePath, UseSmartMerge, OutputFileName, False, PDFMergeSortOrder.Original, False)
    End Function

    ''' <summary>
    ''' Merges multiple PDF files into a single PDF file
    ''' </summary>
    ''' <param name="PDFFilePath">The path in which to search for PDF files to merge</param>
    ''' <param name="OutputFileName">The PDF file to create from the merged PDF files</param>
    ''' <param name="SortOrder">Identifies the order in which to add the source PDF files to the output file</param>
    ''' <returns>A FileInfo object representing the merged PDF if successful. <cref>Nothing</cref> if unsuccessful.</returns>
    Public Overloads Function MergeAll(ByVal PDFFilePath As String, ByVal OutputFileName As String, ByVal SortOrder As PDFMergeSortOrder) As System.IO.FileInfo
        Return MergeAll(PDFFilePath, False, OutputFileName, False, SortOrder, False)
    End Function

    ''' <summary>
    ''' Merges multiple PDF files into a single PDF file
    ''' </summary>
    ''' <param name="PDFFilePath">The path in which to search for PDF files to merge</param>
    ''' <param name="UseSmartMerge">Identifies whether to use a regular <see cref="iTextSharp.text.pdf.PdfCopy"/> or the <see cref="iTextSharp.text.pdf.PdfSmartCopy"/> for merging</param>
    ''' <param name="OutputFileName">The PDF file to create from the merged PDF files</param>
    ''' <param name="SortOrder">Identifies the order in which to add the source PDF files to the output file</param>
    ''' <returns>A FileInfo object representing the merged PDF if successful. <cref>Nothing</cref> if unsuccessful.</returns>
    ''' <remarks>Using the <see cref="iTextSharp.text.pdf.PdfCopy"/> (<paramref name="UseSmartMerge"/> = <c>False</c>) may result in larger files, 
    ''' while using the <see cref="iTextSharp.text.pdf.PdfSmartCopy"/> (<paramref name="UseSmartMerge"/> = <c>True</c>) may result in longer processing times.</remarks>
    Public Overloads Function MergeAll(ByVal PDFFilePath As String, ByVal UseSmartMerge As Boolean, ByVal OutputFileName As String, ByVal SortOrder As PDFMergeSortOrder) As System.IO.FileInfo
        Return MergeAll(PDFFilePath, UseSmartMerge, OutputFileName, False, SortOrder, False)
    End Function

    ''' <summary>
    ''' Merges multiple PDF files into a single PDF file
    ''' </summary>
    ''' <param name="PDFFilePath">The path in which to search for PDF files to merge</param>
    ''' <param name="OutputFileName">The PDF file to create from the merged PDF files</param>
    ''' <param name="RecurseSubFolders">Identifies whether or not to look in subfolders of the specified path for additional PDF files</param>
    ''' <returns>A FileInfo object representing the merged PDF if successful. <cref>Nothing</cref> if unsuccessful.</returns>
    Public Overloads Function MergeAll(ByVal PDFFilePath As String, ByVal OutputFileName As String, ByVal RecurseSubFolders As Boolean) As System.IO.FileInfo
        Return MergeAll(PDFFilePath, False, OutputFileName, False, PDFMergeSortOrder.Original, RecurseSubFolders)
    End Function

    ''' <summary>
    ''' Merges multiple PDF files into a single PDF file
    ''' </summary>
    ''' <param name="PDFFilePath">The path in which to search for PDF files to merge</param>
    ''' <param name="UseSmartMerge">Identifies whether to use a regular <see cref="iTextSharp.text.pdf.PdfCopy"/> or the <see cref="iTextSharp.text.pdf.PdfSmartCopy"/> for merging</param>
    ''' <param name="OutputFileName">The PDF file to create from the merged PDF files</param>
    ''' <param name="RecurseSubFolders">Identifies whether or not to look in subfolders of the specified path for additional PDF files</param>
    ''' <returns>A FileInfo object representing the merged PDF if successful. <cref>Nothing</cref> if unsuccessful.</returns>
    ''' <remarks>Using the <see cref="iTextSharp.text.pdf.PdfCopy"/> (<paramref name="UseSmartMerge"/> = <c>False</c>) may result in larger files, 
    ''' while using the <see cref="iTextSharp.text.pdf.PdfSmartCopy"/> (<paramref name="UseSmartMerge"/> = <c>True</c>) may result in longer processing times.</remarks>
    Public Overloads Function MergeAll(ByVal PDFFilePath As String, ByVal UseSmartMerge As Boolean, ByVal OutputFileName As String, ByVal RecurseSubFolders As Boolean) As System.IO.FileInfo
        Return MergeAll(PDFFilePath, UseSmartMerge, OutputFileName, False, PDFMergeSortOrder.Original, RecurseSubFolders)
    End Function

    ''' <summary>
    ''' Merges multiple PDF files into a single PDF file
    ''' </summary>
    ''' <param name="PDFFilePath">The path in which to search for PDF files to merge</param>
    ''' <param name="OutputFileName">The PDF file to create from the merged PDF files</param>
    ''' <param name="SortOrder">Identifies the order in which to add the source PDF files to the output file</param>
    ''' <param name="RecurseSubFolders">Identifies whether or not to look in subfolders of the specified path for additional PDF files</param>
    ''' <returns>A FileInfo object representing the merged PDF if successful. <cref>Nothing</cref> if unsuccessful.</returns>
    Public Overloads Function MergeAll(ByVal PDFFilePath As String, ByVal OutputFileName As String, ByVal SortOrder As PDFMergeSortOrder, ByVal RecurseSubFolders As Boolean) As System.IO.FileInfo
        Return MergeAll(PDFFilePath, False, OutputFileName, False, SortOrder, RecurseSubFolders)
    End Function

    ''' <summary>
    ''' Merges multiple PDF files into a single PDF file
    ''' </summary>
    ''' <param name="PDFFilePath">The path in which to search for PDF files to merge</param>
    ''' <param name="UseSmartMerge">Identifies whether to use a regular <see cref="iTextSharp.text.pdf.PdfCopy"/> or the <see cref="iTextSharp.text.pdf.PdfSmartCopy"/> for merging</param>
    ''' <param name="OutputFileName">The PDF file to create from the merged PDF files</param>
    ''' <param name="SortOrder">Identifies the order in which to add the source PDF files to the output file</param>
    ''' <param name="RecurseSubFolders">Identifies whether or not to look in subfolders of the specified path for additional PDF files</param>
    ''' <returns>A FileInfo object representing the merged PDF if successful. <c>Nothing</c> if unsuccessful.</returns>
    ''' <remarks>Using the <see cref="iTextSharp.text.pdf.PdfCopy"/> (<paramref name="UseSmartMerge"/> = <c>False</c>) may result in larger files, 
    ''' while using the <see cref="iTextSharp.text.pdf.PdfSmartCopy"/> (<paramref name="UseSmartMerge"/> = <c>True</c>) may result in longer processing times.</remarks>
    Public Overloads Function MergeAll(ByVal PDFFilePath As String, ByVal UseSmartMerge As Boolean, ByVal OutputFileName As String, ByVal SortOrder As PDFMergeSortOrder, ByVal RecurseSubFolders As Boolean) As System.IO.FileInfo
        Return MergeAll(PDFFilePath, UseSmartMerge, OutputFileName, False, SortOrder, RecurseSubFolders)
    End Function

    ''' <summary>
    ''' Merges multiple PDF files into a single PDF file
    ''' </summary>
    ''' <param name="PDFFilePath">The path in which to search for PDF files to merge</param>
    ''' <param name="OutputFileName">The PDF file to create from the merged PDF files</param>
    ''' <param name="OverwriteExistingPDF">If the specified PDF file already exists, identifies whether or not to overwrite the existing file</param>
    ''' <param name="RecurseSubFolders">Identifies whether or not to look in subfolders of the specified path for additional PDF files</param>
    ''' <returns>A FileInfo object representing the merged PDF if successful. <cref>Nothing</cref> if unsuccessful.</returns>
    Public Overloads Function MergeAll(ByVal PDFFilePath As String, ByVal OutputFileName As String, ByVal OverwriteExistingPDF As Boolean, ByVal RecurseSubFolders As Boolean) As System.IO.FileInfo
        Return MergeAll(PDFFilePath, False, OutputFileName, OverwriteExistingPDF, PDFMergeSortOrder.Original, RecurseSubFolders)
    End Function

    ''' <summary>
    ''' Merges multiple PDF files into a single PDF file
    ''' </summary>
    ''' <param name="PDFFilePath">The path in which to search for PDF files to merge</param>
    ''' <param name="UseSmartMerge">Identifies whether to use a regular <see cref="iTextSharp.text.pdf.PdfCopy"/> or the <see cref="iTextSharp.text.pdf.PdfSmartCopy"/> for merging</param>
    ''' <param name="OutputFileName">The PDF file to create from the merged PDF files</param>
    ''' <param name="OverwriteExistingPDF">If the specified PDF file already exists, identifies whether or not to overwrite the existing file</param>
    ''' <param name="RecurseSubFolders">Identifies whether or not to look in subfolders of the specified path for additional PDF files</param>
    ''' <returns>A FileInfo object representing the merged PDF if successful. <cref>Nothing</cref> if unsuccessful.</returns>
    ''' <remarks>Using the <see cref="iTextSharp.text.pdf.PdfCopy"/> (<paramref name="UseSmartMerge"/> = <c>False</c>) may result in larger files, 
    ''' while using the <see cref="iTextSharp.text.pdf.PdfSmartCopy"/> (<paramref name="UseSmartMerge"/> = <c>True</c>) may result in longer processing times.</remarks>
    Public Overloads Function MergeAll(ByVal PDFFilePath As String, ByVal UseSmartMerge As Boolean, ByVal OutputFileName As String, ByVal OverwriteExistingPDF As Boolean, ByVal RecurseSubFolders As Boolean) As System.IO.FileInfo
        Return MergeAll(PDFFilePath, UseSmartMerge, OutputFileName, OverwriteExistingPDF, PDFMergeSortOrder.Original, RecurseSubFolders)
    End Function

    ''' <summary>
    ''' Merges multiple PDF files into a single PDF file
    ''' </summary>
    ''' <param name="PDFFilePath">The path in which to search for PDF files to merge</param>
    ''' <param name="OutputFileName">The PDF file to create from the merged PDF files</param>
    ''' <param name="OverwriteExistingPDF">If the specified PDF file already exists, identifies whether or not to overwrite the existing file</param>
    ''' <param name="SortOrder">Identifies the order in which to add the source PDF files to the output file</param>
    ''' <returns>A FileInfo object representing the merged PDF if successful. <cref>Nothing</cref> if unsuccessful.</returns>
    Public Overloads Function MergeAll(ByVal PDFFilePath As String, ByVal OutputFileName As String, ByVal OverwriteExistingPDF As Boolean, ByVal SortOrder As PDFMergeSortOrder) As System.IO.FileInfo
        Return MergeAll(PDFFilePath, False, OutputFileName, OverwriteExistingPDF, SortOrder, False)
    End Function

    ''' <summary>
    ''' Merges multiple PDF files into a single PDF file
    ''' </summary>
    ''' <param name="PDFFilePath">The path in which to search for PDF files to merge</param>
    ''' <param name="UseSmartMerge">Identifies whether to use a regular <see cref="iTextSharp.text.pdf.PdfCopy"/> or the <see cref="iTextSharp.text.pdf.PdfSmartCopy"/> for merging</param>
    ''' <param name="OutputFileName">The PDF file to create from the merged PDF files</param>
    ''' <param name="OverwriteExistingPDF">If the specified PDF file already exists, identifies whether or not to overwrite the existing file</param>
    ''' <param name="SortOrder">Identifies the order in which to add the source PDF files to the output file</param>
    ''' <param name="RecurseSubFolders">Identifies whether or not to look in subfolders of the specified path for additional PDF files</param>
    ''' <returns>A FileInfo object representing the merged PDF if successful. <cref>Nothing</cref> if unsuccessful.</returns>
    ''' <remarks>Using the <see cref="iTextSharp.text.pdf.PdfCopy"/> (<paramref name="UseSmartMerge"/> = <c>False</c>) may result in larger files, 
    ''' while using the <see cref="iTextSharp.text.pdf.PdfSmartCopy"/> (<paramref name="UseSmartMerge"/> = <c>True</c>) may result in longer processing times.</remarks>
    Public Overloads Function MergeAll(ByVal PDFFilePath As String, ByVal UseSmartMerge As Boolean, ByVal OutputFileName As String, ByVal OverwriteExistingPDF As Boolean, ByVal SortOrder As PDFMergeSortOrder, ByVal RecurseSubFolders As Boolean) As System.IO.FileInfo
        Dim PDFFiles As New List(Of System.IO.FileInfo)
        Dim PDFFolder As New System.IO.DirectoryInfo(PDFFilePath)

        For Each PDF As System.IO.FileInfo In PDFFolder.GetFiles("*.pdf")
            If PDF.Length > 0 Then
                PDFFiles.Add(PDF)
            Else
                Warnings.Add("Empty file : " & PDF.FullName & " not merged into output file.")
            End If
        Next PDF

        If RecurseSubFolders Then
            PDFFiles.AddRange(GetFilesFromSubFoldersForMerge(PDFFolder))
        End If

        Return Merge(PDFFiles, UseSmartMerge, OutputFileName, OverwriteExistingPDF, SortOrder)
    End Function

    ''' <summary>
    ''' Merges multiple PDF files into a single PDF file
    ''' </summary>
    ''' <param name="PDFFileDirectory">The Directory in which to search for PDF files to merge</param>
    ''' <param name="OutputFileName">The PDF file to create from the merged PDF files</param>
    ''' <returns>A FileInfo object representing the merged PDF if successful. <cref>Nothing</cref> if unsuccessful.</returns>
    Public Overloads Function MergeAll(ByVal PDFFileDirectory As System.IO.DirectoryInfo, ByVal OutputFileName As String) As System.IO.FileInfo
        Return MergeAll(PDFFileDirectory, False, OutputFileName, False, PDFMergeSortOrder.Original, False)
    End Function

    ''' <summary>
    ''' Merges multiple PDF files into a single PDF file
    ''' </summary>
    ''' <param name="PDFFileDirectory">The Directory in which to search for PDF files to merge</param>
    ''' <param name="UseSmartMerge">Identifies whether to use a regular <see cref="iTextSharp.text.pdf.PdfCopy"/> or the <see cref="iTextSharp.text.pdf.PdfSmartCopy"/> for merging</param>
    ''' <param name="OutputFileName">The PDF file to create from the merged PDF files</param>
    ''' <returns>A FileInfo object representing the merged PDF if successful. <cref>Nothing</cref> if unsuccessful.</returns>
    ''' <remarks>Using the <see cref="iTextSharp.text.pdf.PdfCopy"/> (<paramref name="UseSmartMerge"/> = <c>False</c>) may result in larger files, 
    ''' while using the <see cref="iTextSharp.text.pdf.PdfSmartCopy"/> (<paramref name="UseSmartMerge"/> = <c>True</c>) may result in longer processing times.</remarks>
    Public Overloads Function MergeAll(ByVal PDFFileDirectory As System.IO.DirectoryInfo, ByVal UseSmartMerge As Boolean, ByVal OutputFileName As String) As System.IO.FileInfo
        Return MergeAll(PDFFileDirectory, UseSmartMerge, OutputFileName, False, PDFMergeSortOrder.Original, False)
    End Function

    ''' <summary>
    ''' Merges multiple PDF files into a single PDF file
    ''' </summary>
    ''' <param name="PDFFileDirectory">The Directory in which to search for PDF files to merge</param>
    ''' <param name="OutputFileName">The PDF file to create from the merged PDF files</param>
    ''' <param name="SortOrder">Identifies the order in which to add the source PDF files to the output file</param>
    ''' <returns>A FileInfo object representing the merged PDF if successful. <cref>Nothing</cref> if unsuccessful.</returns>
    Public Overloads Function MergeAll(ByVal PDFFileDirectory As System.IO.DirectoryInfo, ByVal OutputFileName As String, ByVal SortOrder As PDFMergeSortOrder) As System.IO.FileInfo
        Return MergeAll(PDFFileDirectory, False, OutputFileName, False, SortOrder, False)
    End Function

    ''' <summary>
    ''' Merges multiple PDF files into a single PDF file
    ''' </summary>
    ''' <param name="PDFFileDirectory">The Directory in which to search for PDF files to merge</param>
    ''' <param name="UseSmartMerge">Identifies whether to use a regular <see cref="iTextSharp.text.pdf.PdfCopy"/> or the <see cref="iTextSharp.text.pdf.PdfSmartCopy"/> for merging</param>
    ''' <param name="OutputFileName">The PDF file to create from the merged PDF files</param>
    ''' <param name="SortOrder">Identifies the order in which to add the source PDF files to the output file</param>
    ''' <returns>A FileInfo object representing the merged PDF if successful. <cref>Nothing</cref> if unsuccessful.</returns>
    ''' <remarks>Using the <see cref="iTextSharp.text.pdf.PdfCopy"/> (<paramref name="UseSmartMerge"/> = <c>False</c>) may result in larger files, 
    ''' while using the <see cref="iTextSharp.text.pdf.PdfSmartCopy"/> (<paramref name="UseSmartMerge"/> = <c>True</c>) may result in longer processing times.</remarks>
    Public Overloads Function MergeAll(ByVal PDFFileDirectory As System.IO.DirectoryInfo, ByVal UseSmartMerge As Boolean, ByVal OutputFileName As String, ByVal SortOrder As PDFMergeSortOrder) As System.IO.FileInfo
        Return MergeAll(PDFFileDirectory, UseSmartMerge, OutputFileName, False, SortOrder, False)
    End Function

    ''' <summary>
    ''' Merges multiple PDF files into a single PDF file
    ''' </summary>
    ''' <param name="PDFFileDirectory">The Directory in which to search for PDF files to merge</param>
    ''' <param name="OutputFileName">The PDF file to create from the merged PDF files</param>
    ''' <param name="RecurseSubFolders">Identifies whether or not to look in subfolders of the specified Directory for additional PDF files</param>
    ''' <returns>A FileInfo object representing the merged PDF if successful. <cref>Nothing</cref> if unsuccessful.</returns>
    Public Overloads Function MergeAll(ByVal PDFFileDirectory As System.IO.DirectoryInfo, ByVal OutputFileName As String, ByVal RecurseSubFolders As Boolean) As System.IO.FileInfo
        Return MergeAll(PDFFileDirectory, False, OutputFileName, False, PDFMergeSortOrder.Original, RecurseSubFolders)
    End Function

    ''' <summary>
    ''' Merges multiple PDF files into a single PDF file
    ''' </summary>
    ''' <param name="PDFFileDirectory">The Directory in which to search for PDF files to merge</param>
    ''' <param name="UseSmartMerge">Identifies whether to use a regular <see cref="iTextSharp.text.pdf.PdfCopy"/> or the <see cref="iTextSharp.text.pdf.PdfSmartCopy"/> for merging</param>
    ''' <param name="OutputFileName">The PDF file to create from the merged PDF files</param>
    ''' <param name="RecurseSubFolders">Identifies whether or not to look in subfolders of the specified Directory for additional PDF files</param>
    ''' <returns>A FileInfo object representing the merged PDF if successful. <cref>Nothing</cref> if unsuccessful.</returns>
    ''' <remarks>Using the <see cref="iTextSharp.text.pdf.PdfCopy"/> (<paramref name="UseSmartMerge"/> = <c>False</c>) may result in larger files, 
    ''' while using the <see cref="iTextSharp.text.pdf.PdfSmartCopy"/> (<paramref name="UseSmartMerge"/> = <c>True</c>) may result in longer processing times.</remarks>
    Public Overloads Function MergeAll(ByVal PDFFileDirectory As System.IO.DirectoryInfo, ByVal UseSmartMerge As Boolean, ByVal OutputFileName As String, ByVal RecurseSubFolders As Boolean) As System.IO.FileInfo
        Return MergeAll(PDFFileDirectory, UseSmartMerge, OutputFileName, False, PDFMergeSortOrder.Original, RecurseSubFolders)
    End Function

    ''' <summary>
    ''' Merges multiple PDF files into a single PDF file
    ''' </summary>
    ''' <param name="PDFFileDirectory">The Directory in which to search for PDF files to merge</param>
    ''' <param name="OutputFileName">The PDF file to create from the merged PDF files</param>
    ''' <param name="SortOrder">Identifies the order in which to add the source PDF files to the output file</param>
    ''' <param name="RecurseSubFolders">Identifies whether or not to look in subfolders of the specified Directory for additional PDF files</param>
    ''' <returns>A FileInfo object representing the merged PDF if successful. <cref>Nothing</cref> if unsuccessful.</returns>
    Public Overloads Function MergeAll(ByVal PDFFileDirectory As System.IO.DirectoryInfo, ByVal OutputFileName As String, ByVal SortOrder As PDFMergeSortOrder, ByVal RecurseSubFolders As Boolean) As System.IO.FileInfo
        Return MergeAll(PDFFileDirectory, False, OutputFileName, False, SortOrder, RecurseSubFolders)
    End Function

    ''' <summary>
    ''' Merges multiple PDF files into a single PDF file
    ''' </summary>
    ''' <param name="PDFFileDirectory">The Directory in which to search for PDF files to merge</param>
    ''' <param name="UseSmartMerge">Identifies whether to use a regular <see cref="iTextSharp.text.pdf.PdfCopy"/> or the <see cref="iTextSharp.text.pdf.PdfSmartCopy"/> for merging</param>
    ''' <param name="OutputFileName">The PDF file to create from the merged PDF files</param>
    ''' <param name="SortOrder">Identifies the order in which to add the source PDF files to the output file</param>
    ''' <param name="RecurseSubFolders">Identifies whether or not to look in subfolders of the specified Directory for additional PDF files</param>
    ''' <returns>A FileInfo object representing the merged PDF if successful. <cref>Nothing</cref> if unsuccessful.</returns>
    ''' <remarks>Using the <see cref="iTextSharp.text.pdf.PdfCopy"/> (<paramref name="UseSmartMerge"/> = <c>False</c>) may result in larger files, 
    ''' while using the <see cref="iTextSharp.text.pdf.PdfSmartCopy"/> (<paramref name="UseSmartMerge"/> = <c>True</c>) may result in longer processing times.</remarks>
    Public Overloads Function MergeAll(ByVal PDFFileDirectory As System.IO.DirectoryInfo, ByVal UseSmartMerge As Boolean, ByVal OutputFileName As String, ByVal SortOrder As PDFMergeSortOrder, ByVal RecurseSubFolders As Boolean) As System.IO.FileInfo
        Return MergeAll(PDFFileDirectory, UseSmartMerge, OutputFileName, False, SortOrder, RecurseSubFolders)
    End Function

    ''' <summary>
    ''' Merges multiple PDF files into a single PDF file
    ''' </summary>
    ''' <param name="PDFFileDirectory">The Directory in which to search for PDF files to merge</param>
    ''' <param name="OutputFileName">The PDF file to create from the merged PDF files</param>
    ''' <param name="OverwriteExistingPDF">If the specified PDF file already exists, identifies whether or not to overwrite the existing file</param>
    ''' <param name="RecurseSubFolders">Identifies whether or not to look in subfolders of the specified Directory for additional PDF files</param>
    ''' <returns>A FileInfo object representing the merged PDF if successful. <cref>Nothing</cref> if unsuccessful.</returns>
    Public Overloads Function MergeAll(ByVal PDFFileDirectory As System.IO.DirectoryInfo, ByVal OutputFileName As String, ByVal OverwriteExistingPDF As Boolean, ByVal RecurseSubFolders As Boolean) As System.IO.FileInfo
        Return MergeAll(PDFFileDirectory, False, OutputFileName, OverwriteExistingPDF, PDFMergeSortOrder.Original, RecurseSubFolders)
    End Function

    ''' <summary>
    ''' Merges multiple PDF files into a single PDF file
    ''' </summary>
    ''' <param name="PDFFileDirectory">The Directory in which to search for PDF files to merge</param>
    ''' <param name="UseSmartMerge">Identifies whether to use a regular <see cref="iTextSharp.text.pdf.PdfCopy"/> or the <see cref="iTextSharp.text.pdf.PdfSmartCopy"/> for merging</param>
    ''' <param name="OutputFileName">The PDF file to create from the merged PDF files</param>
    ''' <param name="OverwriteExistingPDF">If the specified PDF file already exists, identifies whether or not to overwrite the existing file</param>
    ''' <param name="RecurseSubFolders">Identifies whether or not to look in subfolders of the specified Directory for additional PDF files</param>
    ''' <returns>A FileInfo object representing the merged PDF if successful. <cref>Nothing</cref> if unsuccessful.</returns>
    ''' <remarks>Using the <see cref="iTextSharp.text.pdf.PdfCopy"/> (<paramref name="UseSmartMerge"/> = <c>False</c>) may result in larger files, 
    ''' while using the <see cref="iTextSharp.text.pdf.PdfSmartCopy"/> (<paramref name="UseSmartMerge"/> = <c>True</c>) may result in longer processing times.</remarks>
    Public Overloads Function MergeAll(ByVal PDFFileDirectory As System.IO.DirectoryInfo, ByVal UseSmartMerge As Boolean, ByVal OutputFileName As String, ByVal OverwriteExistingPDF As Boolean, ByVal RecurseSubFolders As Boolean) As System.IO.FileInfo
        Return MergeAll(PDFFileDirectory, UseSmartMerge, OutputFileName, OverwriteExistingPDF, PDFMergeSortOrder.Original, RecurseSubFolders)
    End Function

    ''' <summary>
    ''' Merges multiple PDF files into a single PDF file
    ''' </summary>
    ''' <param name="PDFFileDirectory">The Directory in which to search for PDF files to merge</param>
    ''' <param name="OutputFileName">The PDF file to create from the merged PDF files</param>
    ''' <param name="OverwriteExistingPDF">If the specified PDF file already exists, identifies whether or not to overwrite the existing file</param>
    ''' <param name="SortOrder">Identifies the order in which to add the source PDF files to the output file</param>
    ''' <returns>A FileInfo object representing the merged PDF if successful. <cref>Nothing</cref> if unsuccessful.</returns>
    Public Overloads Function MergeAll(ByVal PDFFileDirectory As System.IO.DirectoryInfo, ByVal OutputFileName As String, ByVal OverwriteExistingPDF As Boolean, ByVal SortOrder As PDFMergeSortOrder) As System.IO.FileInfo
        Return MergeAll(PDFFileDirectory, False, OutputFileName, OverwriteExistingPDF, SortOrder, False)
    End Function

    ''' <summary>
    ''' Merges multiple PDF files into a single PDF file
    ''' </summary>
    ''' <param name="PDFFileDirectory">The Directory in which to search for PDF files to merge</param>
    ''' <param name="UseSmartMerge">Identifies whether to use a regular <see cref="iTextSharp.text.pdf.PdfCopy"/> or the <see cref="iTextSharp.text.pdf.PdfSmartCopy"/> for merging</param>
    ''' <param name="OutputFileName">The PDF file to create from the merged PDF files</param>
    ''' <param name="OverwriteExistingPDF">If the specified PDF file already exists, identifies whether or not to overwrite the existing file</param>
    ''' <param name="SortOrder">Identifies the order in which to add the source PDF files to the output file</param>
    ''' <returns>A FileInfo object representing the merged PDF if successful. <cref>Nothing</cref> if unsuccessful.</returns>
    ''' <remarks>Using the <see cref="iTextSharp.text.pdf.PdfCopy"/> (<paramref name="UseSmartMerge"/> = <c>False</c>) may result in larger files, 
    ''' while using the <see cref="iTextSharp.text.pdf.PdfSmartCopy"/> (<paramref name="UseSmartMerge"/> = <c>True</c>) may result in longer processing times.</remarks>
    Public Overloads Function MergeAll(ByVal PDFFileDirectory As System.IO.DirectoryInfo, ByVal UseSmartMerge As Boolean, ByVal OutputFileName As String, ByVal OverwriteExistingPDF As Boolean, ByVal SortOrder As PDFMergeSortOrder) As System.IO.FileInfo
        Return MergeAll(PDFFileDirectory, UseSmartMerge, OutputFileName, OverwriteExistingPDF, SortOrder, False)
    End Function

    ''' <summary>
    ''' Merges multiple PDF files into a single PDF file
    ''' </summary>
    ''' <param name="PDFFileDirectory">The Directory in which to search for PDF files to merge</param>
    ''' <param name="UseSmartMerge">Identifies whether to use a regular <see cref="iTextSharp.text.pdf.PdfCopy"/> or the <see cref="iTextSharp.text.pdf.PdfSmartCopy"/> for merging</param>
    ''' <param name="OutputFileName">The PDF file to create from the merged PDF files</param>
    ''' <param name="OverwriteExistingPDF">If the specified PDF file already exists, identifies whether or not to overwrite the existing file</param>
    ''' <param name="SortOrder">Identifies the order in which to add the source PDF files to the output file</param>
    ''' <param name="RecurseSubFolders">Identifies whether or not to look in subfolders of the specified Directory for additional PDF files</param>
    ''' <returns>A FileInfo object representing the merged PDF if successful. <cref>Nothing</cref> if unsuccessful.</returns>
    ''' <remarks>Using the <see cref="iTextSharp.text.pdf.PdfCopy"/> (<paramref name="UseSmartMerge"/> = <c>False</c>) may result in larger files, 
    ''' while using the <see cref="iTextSharp.text.pdf.PdfSmartCopy"/> (<paramref name="UseSmartMerge"/> = <c>True</c>) may result in longer processing times.</remarks>
    Public Overloads Function MergeAll(ByVal PDFFileDirectory As System.IO.DirectoryInfo, ByVal UseSmartMerge As Boolean, ByVal OutputFileName As String, ByVal OverwriteExistingPDF As Boolean, ByVal SortOrder As PDFMergeSortOrder, ByVal RecurseSubFolders As Boolean) As System.IO.FileInfo
        Dim PDFFiles As New List(Of System.IO.FileInfo)

        For Each PDF As System.IO.FileInfo In PDFFileDirectory.GetFiles("*.pdf").OrderBy(Function(f As System.IO.FileInfo) f.LastWriteTime)
            If PDF.Length > 0 Then
                PDFFiles.Add(PDF)
            Else
                Warnings.Add("Empty file : " & PDF.FullName & " not merged into output file.")
            End If
        Next PDF

        If RecurseSubFolders Then
            PDFFiles.AddRange(GetFilesFromSubFoldersForMerge(PDFFileDirectory))
        End If

        Return Merge(PDFFiles, UseSmartMerge, OutputFileName, OverwriteExistingPDF, SortOrder)
    End Function

    ''' <summary>
    ''' Merges multiple PDF files into a single PDF file
    ''' </summary>
    ''' <param name="PDFFileNames">A list of specific PDF files to merge</param>
    ''' <param name="OutputFileName">The PDF file to create from the merged PDF files</param>
    ''' <param name="SortOrder">Identifies the order in which to add the source PDF files to the output file</param>
    ''' <returns>A FileInfo object representing the merged PDF if successful. <cref>Nothing</cref> if unsuccessful.</returns>
    Public Overloads Function Merge(ByVal PDFFileNames As List(Of String), ByVal OutputFileName As String, ByVal SortOrder As PDFMergeSortOrder) As System.IO.FileInfo
        Return Merge(PDFFileNames, False, OutputFileName, False, SortOrder)
    End Function

    ''' <summary>
    ''' Merges multiple PDF files into a single PDF file
    ''' </summary>
    ''' <param name="PDFFileNames">A list of specific PDF files to merge</param>
    ''' <param name="UseSmartMerge">Identifies whether to use a regular <see cref="iTextSharp.text.pdf.PdfCopy"/> or the <see cref="iTextSharp.text.pdf.PdfSmartCopy"/> for merging</param>
    ''' <param name="OutputFileName">The PDF file to create from the merged PDF files</param>
    ''' <param name="SortOrder">Identifies the order in which to add the source PDF files to the output file</param>
    ''' <returns>A FileInfo object representing the merged PDF if successful. <cref>Nothing</cref> if unsuccessful.</returns>
    ''' <remarks>Using the <see cref="iTextSharp.text.pdf.PdfCopy"/> (<paramref name="UseSmartMerge"/> = <c>False</c>) may result in larger files, 
    ''' while using the <see cref="iTextSharp.text.pdf.PdfSmartCopy"/> (<paramref name="UseSmartMerge"/> = <c>True</c>) may result in longer processing times.</remarks>
    Public Overloads Function Merge(ByVal PDFFileNames As List(Of String), ByVal UseSmartMerge As Boolean, ByVal OutputFileName As String, ByVal SortOrder As PDFMergeSortOrder) As System.IO.FileInfo
        Return Merge(PDFFileNames, UseSmartMerge, OutputFileName, False, SortOrder)
    End Function

    ''' <summary>
    ''' Merges multiple PDF files into a single PDF file
    ''' </summary>
    ''' <param name="PDFFileNames">A list of specific PDF files to merge</param>
    ''' <param name="OutputFileName">The PDF file to create from the merged PDF files</param>
    ''' <param name="OverwriteExistingPDF">If the specified PDF file already exists, identifies whether or not to overwrite the existing file</param>
    ''' <returns>A FileInfo object representing the merged PDF if successful. <cref>Nothing</cref> if unsuccessful.</returns>
    Public Overloads Function Merge(ByVal PDFFileNames As List(Of String), ByVal OutputFileName As String, ByVal OverwriteExistingPDF As Boolean) As System.IO.FileInfo
        Return Merge(PDFFileNames, False, OutputFileName, OverwriteExistingPDF, PDFMergeSortOrder.Original)
    End Function

    ''' <summary>
    ''' Merges multiple PDF files into a single PDF file
    ''' </summary>
    ''' <param name="PDFFileNames">A list of specific PDF files to merge</param>
    ''' <param name="UseSmartMerge">Identifies whether to use a regular <see cref="iTextSharp.text.pdf.PdfCopy"/> or the <see cref="iTextSharp.text.pdf.PdfSmartCopy"/> for merging</param>
    ''' <param name="OutputFileName">The PDF file to create from the merged PDF files</param>
    ''' <param name="OverwriteExistingPDF">If the specified PDF file already exists, identifies whether or not to overwrite the existing file</param>
    ''' <returns>A FileInfo object representing the merged PDF if successful. <cref>Nothing</cref> if unsuccessful.</returns>
    ''' <remarks>Using the <see cref="iTextSharp.text.pdf.PdfCopy"/> (<paramref name="UseSmartMerge"/> = <c>False</c>) may result in larger files, 
    ''' while using the <see cref="iTextSharp.text.pdf.PdfSmartCopy"/> (<paramref name="UseSmartMerge"/> = <c>True</c>) may result in longer processing times.</remarks>
    Public Overloads Function Merge(ByVal PDFFileNames As List(Of String), ByVal UseSmartMerge As Boolean, ByVal OutputFileName As String, ByVal OverwriteExistingPDF As Boolean) As System.IO.FileInfo
        Return Merge(PDFFileNames, UseSmartMerge, OutputFileName, OverwriteExistingPDF, PDFMergeSortOrder.Original)
    End Function

    ''' <summary>
    ''' Merges multiple PDF files into a single PDF file
    ''' </summary>
    ''' <param name="PDFFileNames">A list of specific PDF files to merge</param>
    ''' <param name="UseSmartMerge">Identifies whether to use a regular <see cref="iTextSharp.text.pdf.PdfCopy"/> or the <see cref="iTextSharp.text.pdf.PdfSmartCopy"/> for merging</param>
    ''' <param name="OutputFileName">The PDF file to create from the merged PDF files</param>
    ''' <param name="OverwriteExistingPDF">If the specified PDF file already exists, identifies whether or not to overwrite the existing file</param>
    ''' <param name="SortOrder">Identifies the order in which to add the source PDF files to the output file</param>
    ''' <returns>A FileInfo object representing the merged PDF if successful. <cref>Nothing</cref> if unsuccessful.</returns>
    ''' <remarks>Using the <see cref="iTextSharp.text.pdf.PdfCopy"/> (<paramref name="UseSmartMerge"/> = <c>False</c>) may result in larger files, 
    ''' while using the <see cref="iTextSharp.text.pdf.PdfSmartCopy"/> (<paramref name="UseSmartMerge"/> = <c>True</c>) may result in longer processing times.</remarks>
    Public Overloads Function Merge(ByVal PDFFileNames As List(Of String), ByVal UseSmartMerge As Boolean, ByVal OutputFileName As String, ByVal OverwriteExistingPDF As Boolean, ByVal SortOrder As PDFMergeSortOrder) As System.IO.FileInfo
        Dim PDFFiles As New List(Of System.IO.FileInfo)

        For Each PDFName As String In PDFFileNames
            If System.IO.File.Exists(PDFName) Then
                Dim PDF As New System.IO.FileInfo(PDFName)

                If PDF.Length > 0 Then
                    PDFFiles.Add(PDF)
                Else
                    Warnings.Add("Empty file : " & PDF.FullName & " not merged into output file.")
                End If
            End If
        Next PDFName

        Return Merge(PDFFiles, UseSmartMerge, OutputFileName, OverwriteExistingPDF, SortOrder)
    End Function

    ''' <summary>
    ''' Merges multiple PDF files into a single PDF file
    ''' </summary>
    ''' <param name="PDFFiles">A list of specific PDF files to merge</param>
    ''' <param name="OutputFileName">The PDF file to create from the merged PDF files</param>
    ''' <param name="OverwriteExistingPDF">If the specified PDF file already exists, identifies whether or not to overwrite the existing file</param>
    ''' <returns>A FileInfo object representing the merged PDF if successful. <cref>Nothing</cref> if unsuccessful.</returns>
    Public Overloads Function Merge(ByVal PDFFiles As List(Of System.IO.FileInfo), ByVal OutputFileName As String, ByVal OverwriteExistingPDF As Boolean) As System.IO.FileInfo
        Return Merge(PDFFiles, False, OutputFileName, OverwriteExistingPDF, PDFMergeSortOrder.Original)
    End Function

    ''' <summary>
    ''' Merges multiple PDF files into a single PDF file
    ''' </summary>
    ''' <param name="PDFFiles">A list of specific PDF files to merge</param>
    ''' <param name="UseSmartMerge">Identifies whether to use a regular <see cref="iTextSharp.text.pdf.PdfCopy"/> or the <see cref="iTextSharp.text.pdf.PdfSmartCopy"/> for merging</param>
    ''' <param name="OutputFileName">The PDF file to create from the merged PDF files</param>
    ''' <param name="OverwriteExistingPDF">If the specified PDF file already exists, identifies whether or not to overwrite the existing file</param>
    ''' <returns>A FileInfo object representing the merged PDF if successful. <cref>Nothing</cref> if unsuccessful.</returns>
    ''' <remarks>Using the <see cref="iTextSharp.text.pdf.PdfCopy"/> (<paramref name="UseSmartMerge"/> = <c>False</c>) may result in larger files, 
    ''' while using the <see cref="iTextSharp.text.pdf.PdfSmartCopy"/> (<paramref name="UseSmartMerge"/> = <c>True</c>) may result in longer processing times.</remarks>
    Public Overloads Function Merge(ByVal PDFFiles As List(Of System.IO.FileInfo), ByVal UseSmartMerge As Boolean, ByVal OutputFileName As String, ByVal OverwriteExistingPDF As Boolean) As System.IO.FileInfo
        Return Merge(PDFFiles, UseSmartMerge, OutputFileName, OverwriteExistingPDF, PDFMergeSortOrder.Original)
    End Function

    ''' <summary>
    ''' Merges multiple PDF files into a single PDF file
    ''' </summary>
    ''' <param name="PDFFiles">A list of specific PDF files to merge</param>
    ''' <param name="OutputFileName">The PDF file to create from the merged PDF files</param>
    ''' <param name="SortOrder">Identifies the order in which to add the source PDF files to the output file</param>
    ''' <returns>A FileInfo object representing the merged PDF if successful. <cref>Nothing</cref> if unsuccessful.</returns>
    Public Overloads Function Merge(ByVal PDFFiles As List(Of System.IO.FileInfo), ByVal OutputFileName As String, ByVal SortOrder As PDFMergeSortOrder) As System.IO.FileInfo
        Return Merge(PDFFiles, False, OutputFileName, False, SortOrder)
    End Function

    ''' <summary>
    ''' Merges multiple PDF files into a single PDF file
    ''' </summary>
    ''' <param name="PDFFiles">A list of specific PDF files to merge</param>
    ''' <param name="UseSmartMerge">Identifies whether to use a regular <see cref="iTextSharp.text.pdf.PdfCopy"/> or the <see cref="iTextSharp.text.pdf.PdfSmartCopy"/> for merging</param>
    ''' <param name="OutputFileName">The PDF file to create from the merged PDF files</param>
    ''' <param name="SortOrder">Identifies the order in which to add the source PDF files to the output file</param>
    ''' <returns>A FileInfo object representing the merged PDF if successful. <cref>Nothing</cref> if unsuccessful.</returns>
    ''' <remarks>Using the <see cref="iTextSharp.text.pdf.PdfCopy"/> (<paramref name="UseSmartMerge"/> = <c>False</c>) may result in larger files, 
    ''' while using the <see cref="iTextSharp.text.pdf.PdfSmartCopy"/> (<paramref name="UseSmartMerge"/> = <c>True</c>) may result in longer processing times.</remarks>
    Public Overloads Function Merge(ByVal PDFFiles As List(Of System.IO.FileInfo), ByVal UseSmartMerge As Boolean, ByVal OutputFileName As String, ByVal SortOrder As PDFMergeSortOrder) As System.IO.FileInfo
        Return Merge(PDFFiles, UseSmartMerge, OutputFileName, False, SortOrder)
    End Function
#End Region

#Region "MASTER MERGE METHOD"
    ''' <summary>
    ''' Merges multiple PDF files into a single PDF file
    ''' </summary>
    ''' <param name="PDFFiles">A list of specific PDF files to merge</param>
    ''' <param name="OutputFileName">The PDF file to create from the merged PDF files</param>
    ''' <param name="OverwriteExistingPDF">If the specified PDF file already exists, identifies whether or not to overwrite the existing file</param>
    ''' <param name="SortOrder">Identifies the order in which to add the source PDF files to the output file</param>
    ''' <returns>A FileInfo object representing the merged PDF if successful. <cref>Nothing</cref> if unsuccessful.</returns>
    ''' <remarks>Using the <see cref="iTextSharp.text.pdf.PdfCopy"/> (<paramref name="UseSmartMerge"/> = <c>False</c>) may result in larger files, 
    ''' while using the <see cref="iTextSharp.text.pdf.PdfSmartCopy"/> (<paramref name="UseSmartMerge"/> = <c>True</c>) may result in longer processing times.</remarks>
    Public Overloads Function Merge(ByVal PDFFiles As List(Of System.IO.FileInfo), ByVal UseSmartMerge As Boolean, ByVal OutputFileName As String, ByVal OverwriteExistingPDF As Boolean, ByVal SortOrder As PDFMergeSortOrder) As System.IO.FileInfo
        Dim ResultFile As System.IO.FileInfo = Nothing
        Dim SortedList As New List(Of System.IO.FileInfo)
        Dim PDFCopier As iTextSharp.text.pdf.PdfCopy = Nothing
        Dim SmartPDFCopier As iTextSharp.text.pdf.PdfSmartCopy = Nothing

        If OverwriteExistingPDF Then
            If System.IO.File.Exists(OutputFileName) Then
                Try
                    System.IO.File.Delete(OutputFileName)
                Catch ex As Exception
                    Errors.Add("Could not delete existing output file.")
                    Throw
                End Try
            End If
        ElseIf System.IO.File.Exists(OutputFileName) Then
            Errors.Add("Output file already exists.")
            Return Nothing
        End If

        If Not IO.Directory.Exists(New IO.FileInfo(OutputFileName).DirectoryName) Then
            Try
                IO.Directory.CreateDirectory(New IO.FileInfo(OutputFileName).DirectoryName)
            Catch ex As Exception
                Errors.Add("Could not create output directory.")
                Throw
            End Try
        End If

        Select Case SortOrder
            Case PDFMergeSortOrder.Original
                SortedList = PDFFiles
            Case PDFMergeSortOrder.FileDate
                SortedList = PDFFiles.OrderBy(Function(f As System.IO.FileInfo) f.LastWriteTime).ToList
            Case PDFMergeSortOrder.FileName
                SortedList = PDFFiles.OrderBy(Function(f As System.IO.FileInfo) f.Name).ToList
            Case PDFMergeSortOrder.FileNameWithDirectory
                SortedList = PDFFiles.OrderBy(Function(f As System.IO.FileInfo) f.FullName).ToList
        End Select

        Try
            Using OutputPDF As New iTextSharp.text.Document
                Using PDFStream As New System.IO.FileStream(OutputFileName, System.IO.FileMode.OpenOrCreate)
                    If UseSmartMerge Then
                        SmartPDFCopier = New iTextSharp.text.pdf.PdfSmartCopy(OutputPDF, PDFStream)
                    Else
                        PDFCopier = New iTextSharp.text.pdf.PdfCopy(OutputPDF, PDFStream)
                    End If

                    OutputPDF.Open()

                    For Each PDF As System.IO.FileInfo In SortedList
                        Try
                            Using InputReader As New iTextSharp.text.pdf.PdfReader(PDF.FullName)
                                For Page As Integer = 1 To InputReader.NumberOfPages
                                    If UseSmartMerge Then
                                        SmartPDFCopier.AddPage(SmartPDFCopier.GetImportedPage(InputReader, Page))
                                    Else
                                        PDFCopier.AddPage(PDFCopier.GetImportedPage(InputReader, Page))
                                    End If
                                Next Page

                                If InputReader.IsRebuilt Then
                                    Warnings.Add("Damaged PDF: " & PDF.FullName & " repaired and successfully merged into output file.")
                                End If
                            End Using
                        Catch InvalidEx As iTextSharp.text.exceptions.InvalidPdfException
                            'Skip this file
                            Errors.Add("Invalid PDF: " & PDF.FullName & " not merged into output file.")
                        Catch FormatEx As iTextSharp.text.pdf.BadPdfFormatException
                            'Skip this file
                            Errors.Add("Bad PDF Format: " & PDF.FullName & " not merged into output file.")
                        Catch PassworddEx As iTextSharp.text.exceptions.BadPasswordException
                            'Skip this file
                            Errors.Add("Password-protected PDF: " & PDF.FullName & " not merged into output file.")
                        Catch OtherEx As Exception
                            ResultFile = Nothing
                            Errors.Add("Other Error: " & OtherEx.Message & vbCrLf & vbCrLf & PDF.FullName & " not merged into output file.")

                            If System.IO.File.Exists(OutputFileName) Then
                                System.IO.File.Delete(OutputFileName)
                            End If

                            Exit For
                        End Try
                    Next PDF
                End Using
            End Using
        Catch ex As iTextSharp.text.pdf.PdfException
            ResultFile = Nothing
            Errors.Add("iTextSharp Error: " & ex.Message)

            If Not PDFCopier Is Nothing Then
                PDFCopier.Dispose()
            End If

            If Not SmartPDFCopier Is Nothing Then
                SmartPDFCopier.Dispose()
            End If

            If System.IO.File.Exists(OutputFileName) Then
                System.IO.File.Delete(OutputFileName)
            End If

            Throw
        Catch other As Exception
            ResultFile = Nothing
            Errors.Add("Other Error: " & other.Message)

            If Not PDFCopier Is Nothing Then
                PDFCopier.Dispose()
            End If

            If Not SmartPDFCopier Is Nothing Then
                SmartPDFCopier.Dispose()
            End If

            If System.IO.File.Exists(OutputFileName) Then
                System.IO.File.Delete(OutputFileName)
            End If

            Throw
        Finally
            If Not PDFCopier Is Nothing Then
                PDFCopier.Dispose()
            End If

            If Not SmartPDFCopier Is Nothing Then
                SmartPDFCopier.Dispose()
            End If

            If System.IO.File.Exists(OutputFileName) Then
                ResultFile = New System.IO.FileInfo(OutputFileName)

                If ResultFile.Length <= 0 Then
                    ResultFile = Nothing
                    System.IO.File.Delete(OutputFileName)
                End If
            Else
                ResultFile = Nothing
            End If
        End Try

        Return ResultFile
    End Function
#End Region
#End Region

#Region "PRIVATE METHODS"
    ''' <summary>
    ''' Recursive method to find all PDF files in subfolders of a given directory and
    ''' add them to the original list for merging
    ''' </summary>
    ''' <param name="RootFolder">The DirectoryInfo object in which to look for sub-directories containing additional PDF files to merge</param>
    ''' <returns>A list of all the PDF files found in all subfolders of the root</returns>
    Private Function GetFilesFromSubFoldersForMerge(ByVal RootFolder As System.IO.DirectoryInfo) As List(Of System.IO.FileInfo)
        Dim PDFFiles As New List(Of System.IO.FileInfo)

        For Each PDFSubFolder As System.IO.DirectoryInfo In RootFolder.GetDirectories
            For Each PDF As System.IO.FileInfo In PDFSubFolder.GetFiles("*.pdf")
                If PDF.Length > 0 Then
                    PDFFiles.Add(PDF)
                Else
                    Warnings.Add("Empty file : " & PDF.FullName & " not merged into output file.")
                End If
            Next PDF

            PDFFiles.AddRange(GetFilesFromSubFoldersForMerge(PDFSubFolder))
        Next PDFSubFolder

        Return PDFFiles
    End Function
#End Region
#End Region
End Class

EDIT: I found one other little "gotcha" in the "master" method. If the OverwriteExistingPDF parameter is set to False and the file specified by the OutputFileName already exists, I needed to exit the method. I'm not sure if it would be better to generate a new exception object and try to throw that back to the calling method, but, for now I've simply set it to return Nothing. Updated the code in this CW answer to reflect the change.