Location PDFs in Books app 📚 and eksternal backup

Could someone please help me answer the following questions regarding iBooks 🙏

1. Where are all my PDFs stored ? In ICloud ☁️ there are no sign of these documents unlike Pages, Numbers and Photos files 🤔

2. Is it possible, in an easy manner to export all my PDFs to outside of the apple workspace, so I can access them on my PC ?

3. Preferably with the collections /organizational structure I spent much time making In books🤞

Background.

For the last 10 years I’ve been doing voluntary work in a patient organization. Thus , I have over 800 PDFs of research 🤓and all the relevant topics for my work organized with my annotations and highlights in iBooks.

motivation

I’d like to make sure that these do not get lost 🫣

Also I’m considering moving to another PDF reader. Apple Books lacks annotation tools such as those in other apps such as Liquid text, javelin and GoodReader and it does not look like Apple Will be adding any additional features to books as they have not done so for many years.

Best regards Larsr 🤗

[Edited by Moderator]