In Office 365, you can coauthor documents in Word, PowerPoint, and OneNote or a collection of documents with others simultaneously. If you use the Excel Web App (not the desktop version), you can also conduct real-time coauthoring with others. This feature is made possible with the use of SharePoint Online technologies.

For Word and PowerPoint, enable both major and minor version tracking in the document library before you start coauthoring. Doing this lets you keep a history of the document as it goes through the editing phase, roll back to an older version if necessary, and indicate milestones reached in the collaboration process by marking the document as a major version.

Ideally for OneNote notebooks, you should only enable major versions because too many minor versions may cause synchronization errors that can result in lost data. The one drawback to that, however, is that you need to create a separate document library for your OneNote notebooks.

As an alternative, you can limit the number of versions saved to prevent errors. Take into consideration your business needs to determine whether or not both major and minor versions for OneNote notebooks need to be turned on.

When you turn on versioning for a document library, you have the option to enable the Require Check Out feature. If you select Yes under Require documents to be checked out before they are edited?, you are basically saying no one else can edit the document while you have it checked out.

Other users can still view a read-only copy of the document, but they won’t be able to make edits to it and save it back to the document library. Because this is contrary to what you want to achieve when you are coauthoring documents, do not enable this feature.

By default, SharePoint libraries do not have this turned on. Even so, you still have the ability to check out a document from the library and when you do that, no one else will be able to work on the document while you have it checked out.

The Excel Web App 2010 is a cloud version of the desktop application viewable from a web browser in high fidelity, resulting in a visually familiar look and feel as its desktop counterpart. The technology for mathematical computations is the same in web app as it is for the desktop app.

Therefore, regardless of whether you entered the formula in your spreadsheet from the web app or the desktop client, you can get the same results.

Coauthoring in Excel Web App is like magic. You see edits made by your coauthor auto-magically pop up on your screen as soon as your coauthor moves to a different cell. You can see who is editing the spreadsheet by clicking the coauthoring status bar on the lower-right corner of the screen.