Peer Editing format

Community Member

I am using the peer review choice for an essay assignment. I want my students to give feedback on their peers' essays, but they are only have the ability to leave comments in a comment box.  I want them to be able to highlight and drop pins in the assignment.  In watching a peer edit video (from the students' perspective) it says that if "Doc Viewer" has been enabled, they will have the ability to do the tasks that I am requiring.  However, I can't figure out how to turn that on.  Any help???