Earlier this month Microsoft announced that a partnership with Dropbox meant better cloud integration in Office, but that's not the only benefit.
The latest update to Office for Android adds support for Dropbox, as well as better support for Microsoft's own OneDrive cloud services.
Microsoft explained in a blog post that you can now use the Android Office Mobile app to store files on Dropbox, browse files stored there, and edit files directly on Dropbox without having to save them to your device first. You can also email links to Dropbox files from within the app.
The latest update to Office Mobile for Android is available for free (for non-commercial use) from Google Play.