I like to use a skil saw and a good blade. Mark how much needs to come off and score a line with a sharp utility knife several times. Cut door with scored side up which will prevent tearout. Cut at or below the scored line to prevent tearout. If you cut above the scored line the veneer will tear out and leave an ugly unstained spot.
I just did 8 doors for a buddies rental he's fixing up to rent...years of paint and door did'nt shut. Took all of 2 minutes for all 8 doors and my Bostich pwr planer...done and looks great, nice and square with no inclination of blade wobble like I'd typiclly get with a skil saw LOL!!