I've been trying to use the User Access Manager plugin, http://wordpress.org/extend/plugins/user-access-manager/ , and while it seems flexible and powerful for restricting access to pages and posts, I just can't get it working for files. [See earlier unanswered questions in the plugins forum.]
I've looked at the list of plugins at
http://wordpress.org/extend/plugins/tags/restrict and others mentioned in MichaelH's fabulous page:
and don't see others that deal with the files in the uploads folder (but may have missed something).
I'm wondering if anyone has any other plugin recommendations or other suggestions before I go down another path entirely. Thanks!