This is copied from OO help topics.
========
Headers & footers

To access OmniOutliner's header & footer options:

• Select File ‣ Page Setup... to open the page setup sheet.
• In the Settings pop-up menu, select OmniOutliner.
• Click the Headers & Footers tab.

Settings
You can customize headers and footers for certain pages of the outline.

• Use the bottom part of the pop-up menu to set whether the outline's first page should have a different header than the rest of the pages, and whether odd and even pages should have different headers and footers.
• Use the top part of the pop-up menu to choose which pages' headers and footers you would like to customize.

Show
The left, center, and right sections of the headers and footers can be edited separately. Click the one you would like to edit.

Insert
When the insertion point is in the Headers or Footers field, you can use the Insert... menu to create a tag that automatically updates its value whenever the header or footer is printed. These tags include Print Time, Document Title, Page Count, Section Title, Page Number, Last Modification Time, and Document Name.

Headers
Text entered in this field will appear at the top of pages selected in the Settings pop-up menu, in the area selected under Show.

Footers
Text entered in this field will appear at the bottom of pages selected in the Settings pop-up menu, in the area selected under Show.