Put pdf’s in a folder named ~/phosh-ticket-box and they will be available from the lock screen.
If you are, like unfortunately most people nowadays, in constant need of sharing all details of your life realtime with the world, the Librem 5 will never be for you.
It depends. Sharing photos or other files works fine on my Librem 5 with nheko client for Matrix. I heard other messaging clients (even Telegram and Whatsapp, with tinkering) can also be installed.