Problem
I was wondering whether you know how to fix the following issues with the assignment/grading/annotate pdf feature in Lyceum. Two students submitted their assignments in Lyceum as pdf files, but when I clicked on "Grade", I could not see their work (I could see the text of the assignment, but not their answers). However, when I clicked directly on he file that they submitted (and opened it in the browser), I was able to read their answers.
Resolution
The PDF and JPG issues you're encountering are a result of how the students produced the files. In both cases, the issues are specific to Apple products.
If your students add text fields via Preview on a Mac they need to update the change so that the text layer is part of the file: File > "Export as PDF...".
When the file gets exported as a PDF the changes are preserved and are viewable from within Lyceum. If the file is not exported as a PDF what they've added to the file is not viewable from Moodle.
Apple iPhone save image files/photos as .heic format. This format is not handled by Moodle, and it needs to be converted to a .jpg. Often systems or even users will rename .heic files as .jpg (without converting them) and certain devices and systems are able to read them. Moodle, however, can't display .heic files. Safari will convert .heic files to jpg (where as Chrome won't) when uploading the file to a website. Alternatively, students can change the file format setting on their iphones/ipads: Settings > Camera > Formats > Most Compatible.