In an unfortunately sad twist of fate iPhone doesn’t support viewing Apple’s own Pages or Numbers documents. We all realize of course that in this world dominated by Microsoft Office that iWork is a second rate citizen, but it’s particularly bad when Apple treats it that way.
The reason for this, ultimately, is that Pages, Numbers and Keynote files are bundles. A bundle in case you don’t know is actually a folder with files inside of it that appears as a single file in the Finder. This limitation will also preclude support for any Omni application being supported on the iPhone.
UPDATE: iPhone OS 2.0 has support for iWork. Still waiting on Omni(Graffle|Outliner|Project).