Microsoft recently pushed out a small update to OneDrive for Windows Phone devices. The newest version of the app makes it possible to open files from OneDrive in other apps. OneDrive, Microsoft's cloud storage app, is free to download and use.
In what way do they need to offer their (completely unrelated) office suite to make their Cloud highly useful? I use mine all the time, and prefer it over GDrive and Dropbox. Much cleaner and easier to use.