I have a confession to make. PDF Feedback on my site works fine and there is nothing wrong with it. I just messed up when I was testing it out and I didn't really examined in detail your feedback. Pure laziness on my part. And I gave up too soon back then.
BUT I did finally have another stab at getting the plugin to work on my site. Guess what? It works! Actually it was working all the time, it's just that I missed two crucial steps in my haste. Yes, as you had advised, I needed to submit to the "PDF Submission" file manager. I had previously submitted to the File Submission file manager (wrong one) and I had not turned ticked the PDF submission checkbox (tsk! tsk!). and the other trick was to turn "Quick Grading" to on. I can now see the so illusive (to me) "Annotate submission" link. Eureka!!!
I then proceeded to annotate the PDF and generated a response file. From the user point of view, he/she can view the Response File online. So everything is hunky-dory! Yes! Another WOW FACTOR for Moodle. Moodle rocks!!!
Thanks for a great plugin and this is IMHO, a very, if not the very, most useful plugin for teachers to use for students. Provided they have a lightpen or a stylus instead of a mouse to doodle and to 'write' annotations, hehe. Frankie Kam.