Hello, @David Gorman Allegedly there is a way to lock the files so they truly are View Only. Unfortunately, I have never found it to work. Instead, users with that permission setting can't even see the files. However, if you want to experiment get a friend who can be your guinea pig as a Visitor and then:
In your SharePoint site create a Test document library. You can add 'dummy folders' and content you don't care about so you have something to experiment with.
Go to Library Settings and Permissions for this document library. Then, Stop Inheriting Permissions (from the parent). Next, Grant permissions and, at the bottom of the invitation window pick on the inverted caret to display the permission options. Choose Restricted View. According to SharePoint documentation this allows viewing but prevents other actions.
However, as I said before, I have never had any luck using this. The users for whom I've tried to set this level of permission can't see the files - but I hope you have better luck (or someone from MS sees this and gets it fixed! :))
