It's the ones you're not aware of that you need to worry about ;)

Apple PDF and Evince/Poppler are vulnerability-prone C/C++ codebases and have had bugs.

Chrome and Firefox builtin PDF readers are your best bet...

I use Chrome to view PDFs, it isolates the process and doesn't support as many "extensions" as reader, so it is much safer. Works very well.

maybe not alot of the hacker news readers .. but alot of regular people do use Adobe Reader ...