I’m having a very specific need here: I generate PDFs through Photoshop automation, but Photoshop fonts don’t implement fallbacks, so any “exotic” UTF-8 symbols (chinese symbols, mathematic symbols) is a barred rectangle.

Photoshop automation being pretty limited, I had the idea to export the PDF in a way that conserve layers and texts and then, activate character fallback in the PDF itself.
But I can’t find any documentation on how to do that, do you think it’s possible ?
Do PDFs texts even exist as real text or is it just an image with some metadatas ?
Would I be better off modifying the fonts used by photoshop to add all the glyphs of the UTF-8 table ?