When you sign up for Displayr, you get a personal account that only you may access.
At any time, you can choose to convert your account into a multi-user account, and invite other people to join. This enables you to collaborate. See Multi-User Accounts for more details on how to set this up.
You can join someone else's account by requesting an invitation from the account administrator.
The set of documents is shared with everyone in your account. You can set access restrictions to prevent an individual from access certain documents.
Multiple people can edit a document at the same time.
When someone else is editing the same document as you, their initials will appear next to the page that they are editing.