sharing is currently beta
Polar supports sharing files with other users and commenting and sharing annotations and comments allow you to collaborate with groups.
In order to share a document open the document and click on the 'share' button in the sidebar.
At this point a new dialog will open up. Enter the users email to invite them to the document.
You should use their primary Polar email address.
They will then receive a popup notification and they can add the document locally.
At that point all annotations will be shared on the sidebar with each invited user who has added the document.