add free ebook notification

Author: Packt-ITService

README.md

@@ -30,3 +30,7 @@ Matplotlib 2.x
 
 * [Exploratory Data Analysis with Pandas and Python 3.x [Video]](https://www.packtpub.com/application-development/exploratory-data-analysis-pandas-and-python-3x-video?utm_source=github&utm_medium=repository&utm_campaign=9781789959116)
 
+### Download a free PDF
+
+ <i>If you have already purchased a print or Kindle version of this book, you can get a DRM-free PDF version at no cost.<br>Simply click on the link to claim your free PDF.</i>
+<p align="center"> <a href="https://packt.link/free-ebook/9781788839754">https://packt.link/free-ebook/9781788839754 </a> </p>