Finally an iCloud Drive App
Apple finally adds an iCloud Drive app to the iPhone and iPad with iOS 9. This makes it easier to see what is in your iCloud Drive and to interact with the files.
A quick look at the app reveals fast access to documents stored in iCloud, options to download the document or photo to the iPhone and then to open that into another app on the iPhone.
This method is easier than on iOS 8 where the user must be inside an app that supports iCloud and even then that app may not be able to open every file type.