So I'm looking at paid off from no middle ground. If a character is already knelt before an opponent wins an intrigue challenge do they get the option to stand by paying a gold even though paid off was not the effect that knelt them?

Well, no. For quite a few reasons.

First, the owner of Paid off chooses whether or not to trigger the ability, kneeling (and allowing it to stand). If the card is already kneeling, he'd have no reason to trigger it.

Second, as Paid off is a "kneel, THEN X" construction, the Kneel has to be succesful in order for the "Then" portion to matter. So even if he did trigger it, it wouldn't succesfully kneel a character, so that character wouldn't be able to stand.

Third, as triggering Paid Off in that situation would have no effect on the game state, the controller couldn't even attempt to trigger it.

So... definitely no.

Awesome thanks!