I still don't understand how we ended up with PDF as sort of standard to archive data. PDF is already pretty bad for things like manuals but for things like spreadsheets we basically collect the data, then we destroy all the structure by putting it in into POF, and later on we painstakingly try to restore the data from PDF which is often almost impossible to do with accuracy. It just shows that bad solutions often wi…
these are just photos embedded in a PDF, which actually isn't that bad an idea, because it lets you scan multiple pages and join them together as a 'document' (not sure if the documents in OP had several pages, but if you've scanned/photographed a multi-page document, PDF is not that bad of a solution)
It was the standard for scanners until PDF seemed to dominate the scene.