Hello Michael,
as I know this is not documented in the Pages manual. I haven't read the manual (nor version 1 neither version 2) in it's entirety, and I think this is such kind of "feature" the developers are thinking of as a must known one. But in my opinion this counts only for users with experiences in (most) vector image editing and not for the casual/normal user who is just discovering the Pages universe.
But, as I use to write in such situations, for this kind of questions and other problems this wonderful discussion board exists 🙂
