Just photoshop them to contain difficult-to-remove text saying the images are provided for reference only and for that specific school. If they want to advertise you to third parties, it makes it harder for them to pose as a legitimate recruiter.
Oh and I would definitely black out the passport number.
The uni I work for asked for the same documents and they were obviously on the level since I now work there. So it could be legit, or it might not be. Why don’t you google them?