Earlier quoted context omitted.
PDFs can be accessible, and many of them are! Everyone who works with PDF needs to know about PDF/A: https://en.wikipedia.org/wiki/PDF/A PDF/A is a small family of sub-formats to PDFs which amount to the accessible subset of PDF + some requirements. PDF/A and PDF/UA are mandated by a variety of governments for PDF distribution. They're very suitable to archival and are accessible (screenreaders can work with them, th…
PDF/A isn't necessarily accessible. First, PDF is very hard to impossible to scale for people who need big writing, due to reflowing being unavailable or not working properly. Text in PDF/A can still be a big image, e.g. in a scan for archival purposes, if you are "lucky" there is an OCR overlay, but then your screenreader reads OCR'd text which is hit-or-miss. And text ordering is supposed to be "reading order" in P…
If it's scanned copies then all it is is a bunch of images, not A compliant.