Thank you for posting the screenshots with the teacher's and student's view. I don't know why students are unable to download (save) a PDF file when they click on the PDF file of a teacher. Can these students see and download other PDF files from other sites (not Moodle) in the same browser? It may be an Internet browser problem, not a Moodle problem.
Here is what I did.
- started a new Dataform activity
- added field file (settings see below)
- uploaded a PDF file as a teacher
- logged in as student in Mozilla Firefox, clicked on the PDF file and saw the following options (see screenshot):
- I saved the PDF file as a student without any problems.
Can you post a screenshot of a student, clicking on the PDF? What is it that a student will see right after clicking on the PDF file?
With kind regards,