Chevrolet Repair: Low brake pedal, rear brakes, abs brakes

Question
I have a 1997 Blazer with ABS brakes (disc on the front and drum in the back). The brake pedal is low. I have adjusted the rear brakes and the front pads have about half the pad left. Could the ABS system cause the pedal to be low?

Answer
low pedal is usually caused by out of adjustment rear brakes.  adjust to a slight drag when you turn the drum.  

Next thing to try is low master cylinder level.  

Do they go low and if you release and immediately pump them again the come up?  if so, bad master cylinder.