I have mentioned in the comments that you should read the buttons with AnalogRead(). But you can do it other way by simply connecting the buttonpin to digital inputs on arduino(any from 0-13). Analog pins are mostly used for accessing the sensor data as far as I know.I am correcting your code as below:

#include <Stepper.h>

#define STEPS_PER_MOTOR_REVOLUTION 32

#define STEPS_PER_OUTPUT_REVOLUTION 32 * 200 //2048  

Stepper small_stepper(STEPS_PER_MOTOR_REVOLUTION, 9, 8);
int  Steps2Take;
int buttonApin = 4; //connect button to digital pin 4 on arduino
int buttonBpin = 5; //connect button to digital pin 5 on arduino
int dirpin = 8;
int steppin = 9;
void setup()
{
  pinMode(buttonApin, INPUT);
  pinMode(buttonApin, INPUT);
  pinMode(dirpin, OUTPUT);
  pinMode(steppin, OUTPUT);
  small_stepper.setSpeed(1900);
}
void loop()
{
  int valA = digitalRead(buttonApin);

  if (valA == HIGH)
  { digitalWrite(dirpin, HIGH);
    for (int x = 0; x < 100; x++)
    { digitalWrite(steppin, HIGH);
      delayMicroseconds(1000);
      digitalWrite(steppin, LOW);
      delayMicroseconds(1000);
    }
  }
  int valB = digitalRead(buttonBpin);

  if (valB == HIGH)
  {
    digitalWrite(dirpin, LOW);
    for (int x = 0; x < 100; x++)
    {
      digitalWrite(steppin, LOW);
      delayMicroseconds(1000);
      digitalWrite(steppin, HIGH);
      delayMicroseconds(1000);
    }
  }
}

I have mentioned in the comments that you should read the buttons with analogRead(). But you can do it other way by simply connecting the button pin to digital inputs on arduino(any from 0-13). Analog pins are mostly used for accessing the sensor data as far as I know. I am correcting your code as below:

#include <Stepper.h>

#define STEPS_PER_MOTOR_REVOLUTION 32

#define STEPS_PER_OUTPUT_REVOLUTION 32 * 200 //2048  

Stepper small_stepper(STEPS_PER_MOTOR_REVOLUTION, 9, 8);
int  Steps2Take;
int buttonApin = 4; //connect button to digital pin 4 on arduino
int buttonBpin = 5; //connect button to digital pin 5 on arduino
int dirpin = 8;
int steppin = 9;
void setup()
{
  pinMode(buttonApin, INPUT);
  pinMode(buttonApin, INPUT);
  pinMode(dirpin, OUTPUT);
  pinMode(steppin, OUTPUT);
  small_stepper.setSpeed(1900);
}
void loop()
{
  int valA = digitalRead(buttonApin);

  if (valA == HIGH)
  { digitalWrite(dirpin, HIGH);
    for (int x = 0; x < 100; x++)
    { digitalWrite(steppin, HIGH);
      delayMicroseconds(1000);
      digitalWrite(steppin, LOW);
      delayMicroseconds(1000);
    }
  }
  int valB = digitalRead(buttonBpin);

  if (valB == HIGH)
  {
    digitalWrite(dirpin, LOW);
    for (int x = 0; x < 100; x++)
    {
      digitalWrite(steppin, LOW);
      delayMicroseconds(1000);
      digitalWrite(steppin, HIGH);
      delayMicroseconds(1000);
    }
  }
}