I like writing markdown docs with mdbook, though I've never used it for something to be printed physically so I dont know how good/bad PDFs or epubs would come

I like writing markdown docs with mdbook, though I've never used it for something to be printed physically so I dont know how good/bad PDFs or epubs would come out. What I like about it is that its easily extendable. You can write preprocessors to give yourself new features or an entire backend/renderer to render the book differently. I've written a very simple one myself.