.

I'm thinking Print Audit will give a complete trail of printed documents.

We use Print Audit (Ricoh has it re-labeled as PCS Director). You can know everything about each print job except the image itself. Who, what, where, when, how much...over 35 pieces of information on each print job.
You can purchase the software or get it as a SAAS for a monthly fee. The purchase price is based on the number of clients or user licenses where the SAAS model pricing is based on the number of printers that are tracked.

What about PaperCut? I have not sold this software, however I have heard numerous presentations.

There are numerous brand names out there. I Use Print Audit/PCS Director. Papercut I hear is good. It depends on what is best for the client and what needs to be tracked. In addition, some of these have to reside on the PC and some on the print server.