But... the Github wiki of a GitHub repo is a git repo in itself (introduced in August 2010).
You can clone it, push to it or pull from it.
Each wiki is a Git repository, so you're able to push and pull them like anything else.
Each wiki respects the same permissions as the source repository.
Just add ".wiki
" to any repository name in the URL, and you're ready to go.
That makes the "export" part of your question really trivial.
From there, you will find tons of script for converting markdown pages into pdf: