Not long ago, our master bathroom door started sticking, then jamming. It was rubbing the top of the door frame so that the door wouldn't close completely. (Luckily this was the master bath and not the one company used.) The problem grew worse over time. After doing some thinking about the problem, I realized the door wasn't the problem. Neither was moisture.
We had a slim, though heavy, solid wood lingere chest of drawers on the same wall as the bathroom door. The weight of the filled dresser was causing the floor joists to bend under the load. The wall, of course, was following the floor, lowering the door frame, and causing the bathroom door to rub. The floor, not the door, needed to be repaired.
If you have a sticking or rubbing door, don't get mad at it. Don't get out the planer to start shaving the door. Look around. Do you have heavy furniture or cabinets near the door? Your floor joists may need bracing. Sure, you could plane the door and fix the symptom, but you'll have to do it again in a few months because your joists will continue to bend under the weight of whatever caused the problem in the first place.
The traditional method of bracing joists with hydraulic jacks is not for the inexperienced or faint of heart. Take a look for yourself.
Plus, that method has some major shortcomings which I'll discuss soon. But if you are the willing do-it-yourselfer, (or a professional) I have a safe, more effective, inexpensive method that you can use to level floors . It will take some instruction, a little muscle, about $20 per joist being raised, and a cordless drill. If you'll comment on this post that you are interested before the product appears in my store (coming) then I'll let you be one of my free beta testers.