Co-authoring and Versioning
SharePoint Server and SharePoint Online both support co-authoring of Office documents and OneNote notebooks with Office 2016 and Office Online Services.
That means up to 99 people can be editing the same document simultaneously, seeing each other’s edits in real time.
If you plan on using co-authoring with content in SharePoint Libraries, there are a few gotchas to note. 1. OneNote co-authoring uses SharePoint versioning to record changes. Do not enable minor versions on Libraries where you have OneNote notebooks – this can break synchronisation. 2. Each edit made during co-authoring creates another document version. Limit the number of versions kept to keep a handle on space use. SharePoint Online defaults to 500 versions, whereas SharePoint Server does not limit by default. 3. Co-authoring allows multiple authors to edit at the same time. This will not be possible, and co-authoring will be disabled, if you have enabled Require Checkouts on a Library.