You would not want PDF unless you are looking to print it. If you are planning for offline researchability, maybe download the entire website (I mean the /faq/ website)
There is the openbsd.org website in a git repository[1] mirror but the problem here is that you are downloading the entire website, not just the /faq/ folder. But you can use something like downgit[2] [1] https://github.com/openbsd/www/tree/master/faq [2] https://downgit.github.io/ PS: I wish they had the entire faq page as a download somewhere with the source as well, tar'd up.
