Adobe ACROBAT READER 7.0 Manual page 134

Deleting custom stamps
If commenting is enabled in a PDF document, you can delete custom stamps and stamp
categories from the Stamps palette. (You cannot delete the predefined stamps in the
Stamps palette.) When you delete a stamp, the stamp is removed from the Stamp Tool
menu, but the image file is not deleted.
To delete stamps:
1. Choose Show Stamps Palette from the Stamp Tool menu
2. Choose the stamp category, right-click (Windows) or Control-click (Mac OS) the stamp,
and choose Delete from the pop-up menu.
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