Provide a documentation downloadable as PDF

[EmilyGraceSeville7cf]

Description
It would be nice to be able to download a PDF documentation for Pinta for cases when you can't read it online because of unstable internet connection, like I have.

[cameronwhite]

There probably is some way to generate a PDF from the docs, but a workaround for now would just be clone this git repository and run the site locally (https://github.com/PintaProject/user-guide?tab=readme-ov-file#local-testing)