Yes, you can cut off the doors, but there are a couple important things to consider before doing so.
First, many interior prehung doors are hollow. That means that the wood you see around the outside of the door only goes back 1 to 2 inches from the edge. If you cut 4 inches off of a hollow core door, there will be no wood behind where you cut it. You can cut a piece of wood to fit back in between the veneers and glue it if that is the case. If the doors are solid through and through, then this problem is mute.
Now, before you go off and cut the doors, there are a couple more considerations. If you cut 4" off the bottom of the door, the door handles will be 4" closer to the floor. This could be great if you are a very short person, but in most cases this will not be a good thing in both looks and functionality.
Cutting 4" off the bottom of a prehung interior door will also make the bottom set of hinges be very close to the floor.
So what's the fix?...If it is just a door blank and has the door handle already cut, and you haven't routed out the for the hinges yet, you could cut some off the top and bottom of the door. this way, your door handles would not be as low as if you only cut the bottom.
A better option is if you have a full service lumberyard/millworking shop in your town, they may be able to do the cutting of a blank slab for you, then cut the door knob holes to the proper height and also rout out for the door hinges on the door and jambs to the proper height from the floor.
If you were only cutting off 3/4", I'd say that would be a good handyman project. Cutting 4" off the doors is more complicated as you can see.
Unless you are very handy and have a very well equipped home shop, my suggestion would be to either have a local millwork shop cut them for you as I mentioned above, or have a homecenter order special size doors for you.