Make all assignments submitted in PDF capable of annotation.

Many of my online tests and quizzes require that a portion be written and submitted as a PDF. If I set up the test as two parts where one is “file,” I am able to annotate the PDFs submitted. If, however, I set up a single online-only test, students can submit the written portion through the comments feature, but then I cannot annotate the PDF (in Populi). I’d like to have the capability to annotate in Populi any PDF uploaded through the assignment comment area. (Or, perhaps assignment type “test” can be adjusted to accept files in the same way as assignment type “file.“)