Note: This will only work on newly created documents (but you can always cut and paste into a new one).
You are already able to insert "comments" into a document from the Insert menu (or by selecting Ctrl + Alt + M), now just add the person or person's you wish to notify that something has changed or needs changing. The way to do that is by typing the person's email address with an @ symbol in front of it. I have placed an example of how this might look on the right.
This will send an email to the person notifying them that changes have been/need to be made.
This will be tremendously helpful in moving classrooms away from needless paper waste while refining or groups creating a document collaboratively. Now you can leave comments on your student's work and they will be notified what they need to change in order to create beautiful work.
Original Source: Introducing Discussions into Google Docs
Subscribe to BrokenAirplane for great tutorials and educational news.