Export book to pdf

I wrote a very extensive collection of notes with a central note that works as an index and links all the other notes. I typically access them in book mode, and move through the notes using the index on the left. To be able to read them offline (e.g., when traveling) and share them easily I would like to export them as a pdf, but there is no way to do so.

Printing to pdf from the browser results in a (quite ugly) version of my indexing note, where all the links open the hackmd webpage in a browser. What I would like instead is to export the whole book as an atomic pdf, where the internal links move to the corresponding anchor/page in the same document.