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Assignment feedbacks: PDF feedback

Maintained by Davo Davo Smith
This allows a teacher to annotate and return PDF files that have been submitted by students. Teachers can add and position comments and draw lines, ovals, stamps, rectangles and highlights onto the student's work, from within the browser.
Moodle 2.6, 2.7, 2.8, 2.9, 3.0, 3.1

This plugin and the associated feedback plugin, do still, technically, work with Moodle 3.1, but they sit very awkwardly alongside the new grading layout. If you haven't switched over yet, now is the time to do so.

This is part of the PDF annotation plugin for Moodle assignments.

Full instructions and information can be found in the submission part of this assignment plugin at:


This plugin is part of set Assignment: PDF.


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Davo Smith (Lead maintainer)
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  • Picture of J Stringer
    Tue, Apr 16, 2013, 12:31 PM
    Hi Davo,

    I have recently gotten back to setting up our Moodle server and I'm still getting the same errors for PDF Feedback. When I run the command directly on the server it works "/usr/local/bin/gs-X11 -q -sDEVICE=png16m -dSAFER -dBATCH -dNOPAUSE -r100 -dFirstPage=1 -dLastPage=1 -dGraphicsAlphaBits=4 -dTextAlphaBits=4 -sOutputFile="/Applications/MAMP/data/moodle23/temp/assignfeedback_pdf/517e3a15ed98f10c079c7f0873e7c8656a57dbe1/img/image_page1.png" "/Applications/MAMP/data/moodle23/temp/assignfeedback_pdf/517e3a15ed98f10c079c7f0873e7c8656a57dbe1/sub/submission.pdf" 2>&1".

    The png file is generated and saved in "/Applications/MAMP/data/moodle23/temp/assignfeedback_pdf/517e3a15ed98f10c079c7f0873e7c8656a57dbe1/img/"

    When I try through Moodle I get the message "Unable to generate image" "Result: in /usr/lib/libcups.2.dylib". Do you this may have something to do with permissions?

    Thanks again,

  • Davo
    Tue, Apr 16, 2013, 3:19 PM
    I guess it will have something to do with permissions. I have no idea what though. If the command works properly when copied & pasted into the command line and the identical command fails to work when called via PHP, then there must be a problem with your web server configuration or the permissions.
  • Picture of J Stringer
    Tue, Apr 16, 2013, 3:32 PM
    Hi Davo,

    It had something to do with two different versions of the libcups.2.dylib file. One in the MAMP folder the other in the usr folder with GS. I've temporarily replaced the usr folder version with the version from the MAMP folder. It's now working, just hope the switch doesn't cause any unforeseen issues.
  • Picture of Monjur Morshed Bappy
    Sun, Jun 16, 2013, 3:18 PM
    Hi, I install both of PDF Submission and PDF Plugin. When I click Test ghostscript path, it says Internal Server Error.
    any kind of help is appreciated.
  • Davo
    Sun, Jun 16, 2013, 3:50 PM
    Hi. There's no need to post the same message on both parts of the plugin. Please can you turn on debugging on your server and then check for any error messages (either on screen or in you Web server logs).
  • Richard
    Sun, Feb 2, 2014, 12:36 PM
    Since I've installed the PDF Feedback plugin I've been unable to backup my courses in which I've used the plugin. I keep getting an "error/baseelementexisting" when making a backup. I read somewhere that someone thought it was a php error so my tech guys upgraded php to 5.5.8 but I still get the error. I would appreciate any suggestions here. I've got many hours into these courses but no way to back them up.
  • Davo
    Mon, Feb 3, 2014, 4:03 AM
    Richard - I'll see if I can reproduce that error message, but first can you check that backing up a course without any assignments using my plugin works? Also can you check that you can backup a course which uses my plugin by not including that assignment in the backup?

    Turning on debugging on your site ( ), to generate a longer error message, could also be helpful.
  • Richard
    Mon, Feb 3, 2014, 10:24 PM
    Davo, I no longer think it is your plugin, it will not make a backup when I add an assignment to a course no matter the type. Thanks for the quick response. I'll look elsewhere and see what I can find.
  • Picture of Andrew Houston
    Thu, Mar 20, 2014, 6:40 PM
    Hi. Our teachers live the plugin smile I was just wondering though, some of them are using the plugin where students submit the upto assignment 3 times, they have a standard feedback sheet that leaves space for feedback from all 3 attempts. Is there a way to carry feedback across from previous attempts onto the new attempt ?
  • Davo
    Thu, Mar 20, 2014, 7:33 PM
    Andrew - I'm afraid there is no way to carry feedback across from one attempt to the next (the 'create new submission based on last submission' code only supports 'submission' plugins, not feedback plugin). I am not sure it would work well, even if it were supported - if a new submission had a different number of pages from the old submission, or the pages were in a different order, then the feedback would no longer match the pages on which it was found.
  • Picture of John Banner
    Thu, Aug 14, 2014, 10:36 PM
    Is there a way to get the editor to open in a popup window kinda like the built in pdf editor? I tried your plugin because we are using Landscape documents and it works great!
  • Davo
    Thu, Aug 14, 2014, 10:41 PM
    If you want a popup editor, then use the built-in PDF editor (which is based on my plugin) - it is the non-popup nature of my plugin that means it supports landscape documents slightly better.

    I have no plans to add new features to my own version, as I now consider it to have been superseded by being (rewritten and then) integrated into core.
  • Picture of John Banner
    Thu, Aug 14, 2014, 11:09 PM
    Ok thanks! We cannot use the built-in Editor because of the landscape issue, I tried making the documents into portrait but the tables that the students type into do not fit in portrait mode. We will stick with this plugin until Moodle's built-in supports Lanscape documents.
  • Picture of Gaylen Urie
    Sun, Aug 24, 2014, 10:12 PM
    This plugin is awesome, but I am wondering if there is a way to force the feedback window into full screen. I am wanting to be able to annotate the file on an ipad. It works, but it moves the window rather than writing on the page.

    Any suggestions?
  • Davo
    Mon, Aug 25, 2014, 4:31 PM
    Gaylen, now that this functionality has been integrated into Moodle core (2.6 onwards), I do not intend to add any more features to my version. Please try out the core version, then open an issue on, if you would like to see an improvement there.
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