In the cases of shifting framing, we use the operation of the door itself as a gauge to show us what part of the structure of the building needs attention, and how much; if the hinge side of the door has dropped, then the knob side will tend to rub on the floor; if the latching side of the door (the doorknob side) has dropped, the door will bind at the upper corner on the knob side of the door. Sometimes multiple doors in a section of a house are off and when that is the case, usually some floor lifting as leveling solves the doors at the same time!