Apple Books don't sync to iCloud
When I add a PDF to the Books app in MacOS the file isn't uploaded to iCloud, even though it should be (according to the settings). I'm logged in to all my devices with the same Apple ID, but the file is not available anywhere else than locally on the Mac where it was imported.
I have tried to log in/out and to turn off/on iCloud storage for the app, but nothing helps. Does anyone have an idea of what may be wrong?
MacBook Pro