How do I go about re-plumbing an interior bathroom door that is rubbing at top corner opposite the hinge side ?

Do you actually want to replumb the entire door or just plane down the high, much easier. Replumbing requires you to remove the door trim on both sides of the frame. Once removed you can can see and also cut the nails holding the jam in the door frame, remove all shims. Plumb hinge side of jam with little or no shims then move to the lock side of the door. Shim the jam so it is evenly spaced off the door by 1/8" and then nail to the frame. Lots of work when most folks just plane down the top of the door.

You could take a scrap piece of 2x4 and hammer the top edge of the jamb until the door doesn't hit. If you want to protect the jamb cover the 2x4 in a dish towel.

Patty, won't that cause the side of the jam to pretty much stay in place and just let the top cros piece separate from the side and make a gap? The side of the jam will not slide or slip upward, it is shimmed and nailed.

It will help him from having to cut the door. He could put a chisel under the side jamb and try to pry it back up and shim it.

Can't re-shim with the trim still on the frame. Lets pass on this until Stven gets back to us to say if he really wants to change the frame or just trim the door. I do my triming frequently with a electric planer or belt sander, very quick

How about just re hang the door properly?how old is the door?Is it a split jamb? That's what I would do let me know I will walk you through the steps of dismantling the door and jamb as to not damaging any thing especially the sheetrock around the entire trim