Microsoft has released an update for Office 2016 for Mac (v16.9) that adds real-time multi-user editing to Word, Excel, and PowerPoint.  When more than one person is editing a document simultaneously, a thumbnail will show in the upper right corner of the app indicating someone else is working on the doc.

Microsoft describes this feature as “Edit with others in real time: Thumbnails in the upper-right corner of the window show who else is working with you in a shared document. Flag icons show where others are working and you can view changes as they type.”