I’m not sure that anything the President signed at this point would be worth much. She’s in so much trouble that a pardon from her isn’t going to be worth the paper it was written on.
IRL, the power to pardon is absolute. Conceivably, a president could be prosecuted if they, oh, let's say sold a pardon to a group of terrorists for a campaign contribution to his wife, but that wouldn't undo the pardon.