Gentoo users might benefit if they were able to install relevant Gentoo documentation (Handbook, devmanual, wiki.g.o etc) on their Gentoo systems for offline use. I suggest creating ebuilds for official Gentoo documentation or a special tool for downloading Gentoo related documentation automatically or a gentoo-docs-9999.ebuild to do the same. PS: I noticed that the devmanual is already provided by app-doc/devmanual.
Wiki pages could be exported to pdf using a mediawiki extension: https://www.mediawiki.org/wiki/Extension:Collection
It's probably a good idea to bring this up on the developer or project mailing list.
app-doc/devmanual is available for quite some time