Apple Aperture 2 - Manual (Page 497)

Chapter 17 Exporting Your Images 497
IV
To create a new name format:
1 Select an image in the Browser.
2 Choose File > Export > Version (or press Command-Shift-E).
3 Choose Edit from the Name Format pop-up menu.
The Naming Presets dialog appears.
4 In the Name list, select an existing name format on which to base the new name
format, then click the Add (+) button.
A copy of the selected name format is created.
5 Rename the new name format.
Select an existing name
format in this list.
Click the Add button.