If you open a PDF, that should never lead to RCE, but that's not the world we live in. Better for tools not to open PDFs when you don't expect that to happen.
If I open a PDF in a full-featured reader, I'm slightly ill at ease. If I sha256sum it or wc it, I should be (read: ought to be, in any sane world) perfectly at ease. No matter how complicated the data structures in it, they shouldn't affect those programs.