Install and enable the attached fileconverter plugin (it would be prudent to do this on a fresh install): Extract the contents of the zip to files/convert Browse to "Site administration > Plugins > Document converters > Manage document converters" and open the eye on the "Dummy" converter - ensure all other converters are disabled Create an assignment with file submissions enabled As a student submit a png or jpg file for the assignment Log back in as admin and ensure you have your browser's network monitor open Grade the assignment submitted previously Verify you see multiple requests to a URL that looks like mod/assign/feedback/editpdf/ajax.php?sesskey=zeduN5kMkx&action=pollconversions&userid=3&attemptnumber=0&assignmentid=1&readonly=0 (action=pollconversions is the important part) NB: The dummy plugin reports that a file was converted randomly (1 in 5 chance) so it's possible you will only see one request to that URL. If that happens run through the steps again with a different student until you see the URL polled like 4 or 5 times. Verify you see a handsome lad after the conversion is finished