How many kinds of secret are there?
How many different classifications of document should you have?
The answer: two.
Documents should be "public" or "private".
Public documents need not necessarily be published public documents, but contain information that is not important to keep from the public. By fact, any document that has been published is already public, no matter what you'd like it to be.
Private documents should be attached to an explicit or implicit list of people who are entitled to view them, and there should be policies, procedures, practices and phreakin' ACLs in place to make sure that their privacy is not broken.
Can you think of a document secrecy category that isn't covered by this?