Let me put it this way...

In one of my penetration testing training classes, in one of the lessons, we generated a malicious PDF file that would give us a shell when the victim opened it in Adobe.

Granted, it relied on a specific bug in the JavaScript engine of Adobe Reader, so unless they're using a version that's 15 years old, it wouldn't work today, but you can't be too cautious. 0-days can always exist.

Yes, opening random pdfs especially in random and old pdf viewers is not a good idea.

If you must open a possibly infected pdf, then do it in browser, pdf.js is considered mostly safe, and updated.

Use the PDF to JPG online services, convenient and you still get your result without having to deal with any sandbox

Except of course that you're sharing the contents of that PDF with a random online service.

True, I just considered that once you handle a PDF with so much care like if it was poisoned, it's perhaps better to send this poison to someone else to handle.