Need to store user specific info tied to doc id. What is the recommended way to do this?

I have a doc database with documents having multiple versions.
The users can subscribe to a doc (watch it), they can rate the documents, add their own tags, visible to them only, add more versions (edit the doc and save it) and so on. I also need to keep the date when the user last accessed the document and the date when he is planning to do that again (access it)
I need to be able to quickly retrieve all the docs that a user subscribed to, with all the info particular to that document.
It seems more appropriate to me to store this in a SQL like db (rdbms) …am I wrong. can this be done efficiently in MongoDB? If not are there any docs that you would recommend me to read in order to understand how to properly set this up?

thank you

Start with

thank you that was what I needed