Hello Zyttrio,
Thanks for reaching out and for your interest in CryptPad!
What you describe isn't possible due to the very nature of end-to-end encryption. Each file is given a unique identifier upon creation, before being uploaded to the server. Every setting you apply to this file will be referenced with the identifier I just mentioned. So, if you upload another PDF, it'll have another identifier.
A way to achieve what you'd like is by leveraging folders. You can create a shared folder and upload PDF files in it. Then, modifying the files won't impact the folder itself, the preferences (sharing, access rights, etc) will remain the same.
Please see the folders section of the user guide to know more about it: https://docs.cryptpad.org/en/user_guide/drive.html#folders
Hope this helps! 😊
