Office for Mac now lets you co-author in real time just like the online version! (Read more at Arstechnica.) To enable this functionality, update your Office apps by opening any of them, go to the Help menu, and choose Check for Updates. After updating, you will be able to open documents and change them with other people at the same time. Note that the other users ALSO need to be on the latest version if they are also using the Mac apps.