I haven't had an opportunity to try PDM Standard yet but I would think it can work with AutoCAD files. As you say they are DWG files. The add-in for AutoCAD allows PDM functions inside AutoCAD which is probably not compatible with Standard. I think you can still use the Windows Explorer interface to work with DWG files in PDM Standard.
Hi Jonathan, as Michael says, you could most likely use PDM Standard to manage DWG files regardless of whether they come from Draftsight or AutoCad. You would just have to use Windows Explorer to do all the data management functions (check in/out, change state etc)
PDM Professional comes with a plug-in for Autocad, that brings those functions within the Autocad interface.
Michael and Prasad, thanks for your input.