I think that using a dedicated air-gapped machine just for opening PDFs is a bit much if you don’t rely on assistive technologies to read PDFs. A much less nuclear option: Qubes OS has an excellent PDF converter to convert PDFs to safe bitmaps, and back into PDFs. The results are completely inaccessible, so I wouldn’t recommend sharing the final artifacts; however, this approach is fine for personal use.
The Qubes blog covers this in more detail: Converting untrusted PDFs into trusted ones: The Qubes Way, by
SaaS can actually be helpful when it comes to processing potentially-malicious files. In high school, we had to make heavy use of Google Drive. One approach that I used to use was to open a PDF with Google Docs and export the resulting Google Doc.