It depends on which side of the door you are working from. If you are working in the room that the door closes on, position the Door Anchor in the center of the door and you shouldn't have any problems at all as you would have to pull the wall down in order for it to fail :-)
If you are working in the room that the door opens into, the integrity of the door becomes more important. A big fire door you should still be able to work from the middle of it. If you are at all concerned position the door anchor above the hinges and you will be good. Hollow core light weight doors are to be avoided if possible.
Check out the video below for details