Thank you for your question, as the workaround to it helps indeed, not only in iWorks but also in other iCloud document viewing and editing apps (see below). I shall post the following nevertheless to help Apple's guys to solve this "64bits-backboardd-iCloud" problem ...
Probably all inked to 64 bits ... and to the clipboard ... My first clipboard entry when I started with my 5S is always coming back somehow into the clipboard after a few minutes, annoying ... and I suspect a link ...
If you look into the diagnosis section in the information section in the general section of the preferences, you will find laboriously that most kernel panics causing a reset were provoqued by a daemon named "backboardd", apart from one exception I found so far, the application "DataMan Enterprise" which caused crashes without "help" from "backboardd" when active or in the background, of course, I dumped that application, sorry for the developers of otherwise reliable applications.
The other applications, leading systematically, in certain constellations, to crashes, mostly after having been sent to background, were "Pages" (after speaking a text passage), "GoodReader" and "PDF Expert" (when reading a 1000 pages document off the iCloud). All these resets were logged as due to "backboardd" causing a kernel panic.