PDFs are tricky... these are an encapsulated file, not a webpage... Typically, Adobe Analytics tracks the opening of "pdfs" by tracking the click action (as a "download" type) on links that open specific files (as listed by you - there is a default list that includes pdf)

There is no tracking inside the PDF itself.
You cannot embed JavaScript inside a PDF... in theory, you could go back to the old days, and essentially create a hard code "noscript" tracking pixel to embed inside of each PDF, but this will add significant overhead on the people creating the PDFs, assuming you can even get them to reliably do this step every time.. plus having to go back and update every existing PDF in your system.
Each pixel would need to be crafted to provide enough detail to identify the file, and since it would be hard-coded with no scripting, you wouldn't be able to get any reliable UV data... and if your site has any sort of an opt-out function, you may need to check if you have any legal issues with this kind of hard-coded solution, as there would be no opt-out available....
Unfortunately, my recommendation is that this is just the nature of PDFs and you won't be able to get any data.