A Guest role can get View online, Download secured PDF and Download original permissions. These permissions can be set to a document level.
Permission report: A Guest can download a permission report in the Reports section to find out what kind of content permissions their Guest role has.
Activity reports: When granted report permissions a Guest role can see the activities of all users in the same role.
Example for a Guest role: Users in this role are representing a potential buyer group and may view all documents in the Vault online.