I've really begun to love the PDF annotation tool for reviewing student work.  It is a great way to provide formative feedback to students.  
 I am in need of the opposite of the tool.  I need pdf annotation on the student side of the assignment.  I would like to assign a PDF on which the student is to record their responses (by annotating) before submitting for grading.   
Currently students are downloading the file, annotating locally and then uploading back to the assignment page.  This is cumbersome and has proven difficult given the number of devices students can be using.   Some students are using https://www.pdfescape.com with success but they still have to download and upload each file.    Having this baked into Moodle would be amazing.