I upgraded to iCloud drive some time ago. So, that isn't an issue for me.
I am having an issue accessing my Pages documents from the
iCloud drive app on iOS9. Using the iCloud drive app, I can find Pages documents, but when I try to open the Pages document using the share icon, Pages is not provided as an option. So, it seems the iCloud app does not want me accessing a Pages document indirectly, and prefers that I hit the home button and launch the Pages app to open the document. Not sure why the iCloud app refuses to let me open-in Pages.
What is really weird is that i can access Numbers and Keynote from the iCloud app. However, it does not provide an "Open-in" option. Rather, for Numbers and Keynote, I am allowed to "Copy to" those apps from the iCloud drive app. So, basically, I end up with a duplicate file in iCloud when trying to open from the iCloud app.
Frankly, the iCloud drive app seems half-baked and amateurish. Or, I might be doing something wrong. In which case, I am half-baked and amateurish.....which I can live with!