Hello,
first of all, I think this question was asked before in a similiar way. But I am a Processwire newbie and just don't understand all of the posts I have read before.
My idea is to create pages for users and in that pages (in the frontend) are attached documents, which I attach from the backend. The user should not edit anything in the backend and should only be allowed to see a destined page in the frontend. Perhaps this could be realized with sites that have the name of the user.
mypage/user1
mypage/user2
The sites are not visible to anyone else. So when user1 logs in via processwire backend, he cannot edit anything, but can open the URL
mypage/user1 and sees the frontend, where he can download files attached to it.
Thank you very much!