I had the same problem with 5 doors in our 2 yr old house. I planed the
doors with a power planer because there was too much to plan by hand.

My suggestion is to scribe a line down the door before you plane. This
way you will get an even gap between the door and the frame. If you
power plan it, scrape the paint off the edge first. The paint will
cause a knick in you blade.

Good luck.