I had this as well in one of my projects, I tried to stop plotting and held Esc till it quit. Yeah never doing that again. Ok so this is an error in your database and the way that I was combating it was running the Publish command and finding which dwg that was not pdfing. i would then remove the dwg from the project, delete the dwg and restore using a .bak file. Then I would add the drawing back to the project. This only worked for like a day though, but it stopped throwing up the error.
![Autodesk Design & Make Report](https://forums.autodesk.com/t5/image/serverpage/image-id/1350519iCB55845EBFC43016/image-size/large?v=v2&px=999" "Autodesk Design & Make Report")
