So if you receive a pdf full of sections containing prerasterized text (e.g adverts, 3d rendered text with image effects, scanned documents, handwritten errata), what do you do? You cannot use OCR because apparently only pdf-illiterate idiots would try such a thing?
I wouldn't start by rastering the rest of the PDF. In business world, unlike academia and bootleg books and file sharing, majority of PDFs are computer generated. I know because I do this for a living.