in reply to User Who Modified File
What type of files are you tracking? Are you tracking Office files? What about PDF files? Or are you tracking any file submitted?
To track Office (2007=<) files you can query the internal XML file (docProp -> core.xml) for the lastModifiedBy and dcterms:modified flags. This will give you the date of modification and the actual name of the person you modified the file, not just the name of the person who uploaded the file to the CMS. These properties are st every time the file is touched.
PDF files also have a document properties that can be queried by PDF::API2 using the $pdf->info(%infohash) function. Most of these properties have to be set when you create the document.