When you add a user as an approver or a reviewer to a document, they will receive an email when you make a change to that document. As long as the users have permissions to access the space, they should be able to view to document using the links provided in the notification email.
Unfortunately, we do not support the ability to specify a group in the document collaboration area, so you have you specify each user individually. We have this improvement on our road map and will hopefully get it in soon.
In this case, my question was relative to a discussion, rather than a collaboration.
I would like to invite specific users to participate in a discussion and have found no way to do this.
Is there a way?
Currently I send an email out to the people with the link I want them to go to. That or IM them the link.
This is a cumbersome model, and I know the development team is working on a "notification system" of new content, however it is still in the design phase.