If you mean a 32" rough opening (meaning no door jamb), then a 30" door would work. If you have a door jamb, then a 32" door.
34"opening
you have to have a 34'' opening
34'' opening
You have a 34" rough opening (meaning no door jamb)?
Then you need a 32" door. Figure the jamb will take up about 1 1/4". That gives you 3/8" on each side to shim. It's a little less than ideal but should work, especially if the framing is reasonable plumb.