Well that's annoying. It's not working on my iPad either. Just starts and never finishes; though at least I can cancel it, most of the time.
I was just considering working on a Word document in Pages, because I'm more familiar with the app. I guess I'll use the Word app after all. I signed up for a free Microsoft account today, because I wanted to see how that document would look.
The iWorks apps were last updated 15 Sept, just days before the iOS 9 release. I'd have expected them to be iOS 9 ready; though to be fair nothing in the release notes says they are. And they don't show up in the slide over (multitasking) panel; so maybe Apple's still working on them.
I'm going to test the conversion on the Mac and in iCloud.com, to see if you've got options. Back shortly.