I'm a happy Dropbox user: http://www.getdropbox.com
PM me for a referral code and we'll both get a little bit more space for free.
It won't actually store the content on your iPhone (it will on Mac, Linux, Winders), but there's a reasonably convenient web interface, it's fast, and the price is right (free).
You can set up PDF options in the print dialog to send your printout to a PDF file in a place of your choosing (such as your Dropbox folder) which will make it a quick operation. http://www.macosxtips.co.uk/index_fi...-services.html
At that point, it's just cmd-P to bring up the print dialog, a click on the PDF button to bring up the menu, choose the Dropbox alias, and the PDF file should be accessible from the iPhone as soon as Dropbox finishes the upload to their server.
I also use Air Sharing (was free when I grabbed it, but normally isn't), which does store content on the iPhone/iPod. As I have an iPod and usable WiFi is not ubiquitous, sometimes I need to take that route. It is somewhat less convenient, as you have to launch the app, then mount the AFP server it runs from the Mac, and copy your content over. If the iPod goes to sleep while you are doing this, the Mac gets cranky.
Yet another option: if your OmniOutliner document only has one column, you can import it into OmniFocus and move the stuff out of the Inbox into a project. That will allow you to do some editing, too! Only useful if you have OmniFocus on desktop and iPhone/iPod, of course.