Isn’t it just far easier to transfer documents using one of the thousands of cloud apps though? Since Dropbox and such became a thing I’ve not had a use for USBs. If it’s privacy that concerns you then you already mentioned self hosted services and I’m sure there’s a few Dropbox clones among them.
There’s not much point in survival PDFs unless you’re also carrying a laptop to view them on.
If you really do want to go full apocalypse prepper then track down an archive of Wikipedia and various how-to websites.