So I looked into the Repository module and the Documents module. Unfortunately, I don't think they help my situation. It seems like both modules suppress showing a document link if you don't have permissions, rather than allowing you to see the link, and then prompting to login if you click on it.
Even if I found out how to do this, if the user is ever able to get the full URL to the file in the document library, they can then always access it through this URL, circumventing any permission settings through DNN.
Am I missing a way to protect a file from URL access without forcing a DNN login?
Thanks,Dave