I’d imagine by checking that text is in the drawable area of the PDF, above some font size, at the maximum z height, colour different from the background, etc e

I’d imagine by checking that text is in the drawable area of the PDF, above some font size, at the maximum z height, colour different from the background, etc etc etc. Though I think this sort of prompt injection is actually very difficult to parse for solely because you could also just put it into a body of text. Your recruiter is only skimming your resume, a quick parenthetical in the middle of a paragraph won’t be noticed. Will get a chuckle at the interview though, but now you have a foot in the door!