Strictly anecdotally, I've had no trouble feeding PDFs to OpenAI's bot.

The searchable PDFs get searched, and the just-pictures-of-words ones get fed through their (quite good, IMHO) OCR.

I use it all the time. It's remarkably good for locating the details I need in the poorly-organized ~1,200 page factory manual for my Honda.

(Well, it's not necessarily organized poorly. It's just designed with the clear intent that it is mostly to serve as a set of repair instructions, and sometimes I don't want repair instructions. Sometimes I want to know how a thing works for my own cognitive benefit instead of how diagnose and R&R it as a series of steps.)