Rights Management Administrator administers documents that has rights management. The users can set a level of protection on the document.
The Administrator will not be able to view or edit the document. The Rights Management Administrator can assign a super user who has the ability to view or edit any document.
A point to note is that neither the Rights Management nor the super user function is enabled by default. The Global Administrator has to first enable Rights Management using the Office 365 Admin panel. And if he wants he can assign a Rights Management Administrator.