There are two types of PDF (probably more, but hey I'm only a doc).
There are, in effect, searchable and non searchable.
The former include the actual text embedded in the file, and are often PDFs created by programs like Word ( and some print to PDF utilities) and of course Adobe. They are usually smaller in size.
The latter are just images ( in TIFF format ). It is these that need to be OCR'd, they come from fax machines and scanners, etc. most of your items will be these.
there are (having seen web sites for) utilities that turn the image only into searchable. They OCR the image and embedded the text, but remain PDF files.
PDF files are not tamper proof (witness POTUS birth certificate), so the security of medical records is really moot.
