http://piratepad.net will allow you to upload a paper OR type a document and have real-time editors or contributors. Each collaborator chooses their own text color so that everyone knows what they contributed or what they chose to edit. You can chat on the side and discuss changes that need to be made BEFORE you make them to the document. The document can be saved, printed, and shared. Teachers have access to this site, but students will need to have teachers bypass for them on this site because of the chat feature. Because there is a chat feature, please remind your students that all conversations are logged and inappropriate comments are presecutable (local, state, and federal). This is a fantastic tool to use when collaborating on a composition of any type (ie poetry, research paper, handbook, policy, etc). If you need help, email me.
    Here is an example of an active Pad: http://piratepad.net/7SsvmXldNU
    Here is YOUR assignment: http://piratepad.net/YoqPFIilRq