Not sure about the floor jack idea being good in all cases.
If the door is low in the back and you have a good, even gap along the leading edge, jacking up the back of the door is going to tighten the leading edge gap at the top. True, you could cut the leading edge of the door to even out the gap but that's something I would avoid. Seems to me that method changes the hinge geometry.
The trailing end of my driver door was low by about 3/4 inch but I had a good gap on the leading edge so I pulled the hinge pillar forward at the top hinge and everything fell into place because the opening was out of whack.
HERE'S a picture of my Rube Goldberg come-along. Of course, I had the advantage of no cowls or floorpan to fight with.
Your bodyman friend has trained eyes and knew what to do in your specific case and although it worked then, it may not be what you need.
Study your situation carefully before proceeding. I don't cut or bend anything until after I have completely mulled it over in my head a hundred times considering all the possible repercussions, and even then things seldom go according to plan. But it does reduce the possible things that could go wrong.