Create an assignment with assignsubmission_file and assignfeedback_editpdf enabled. As a student, submit a file (of a format that can be converted to PDF). As a teacher, annotate the generated PDF with comments, using various background colours, over some existing text. Make sure all the comments added appear semi-transparent. Release the feedback. As a student, view the annotated PDF. Make sure all comments appear semi-transparent. Download the annotated PDF and open it offline. Make sure all comments appear semi-transparent in the downloaded PDF.