One of the questions folks have been asking recently concerns the use of the new, universal Microsoft Office apps for Windows 10 and whether or not you'll need Office 365 to edit documents. Microsoft initially said that access would be free for mobile devices and today that is being cleared up once and for all.
In short, you can't use these, free apps on a PC or large tablet to edit documents without an Office 365 subscription.
Full story from the WindowsCentral blog...