There's a notes field in OmniOutliner, are you referring to that, or a column you added to keep notes?
OmniOutliner for iPad does not allow you to have anything to the left of the Topic and Status columns. OmniOutliner for Mac does not have that restriction.
The OmniOutliner notes field on the Mac can be displayed "inline" (as it is in my example) or in a pane at the bottom of the window. No such option for the iPad version.
You should be able to email documents back and forth in OmniOutliner format. You might check to make sure that you've got the latest version of the iPad app, as they recently fixed a bug in the handling of files sent to the iPad by email.