Adobe ACROBAT READER 7.0 Manual page 102

Deleting custom stamps
Use the Stamps palette to delete custom stamps and stamp categories. You can delete only
custom stamps that you created, not the predefined stamps. When you delete a stamp, the
stamp is removed from the Stamp Tool menu, but the stamp file is not deleted.
To delete stamps:
1. From the Stamp Tool menu
2. Choose the stamp category, and then right-click (Windows) or Control-click (Mac OS) the
stamp, and choose Delete from the pop-up menu.
Note: Deleting all stamps in a custom stamp category deletes the custom category.
on the Commenting toolbar, choose Show Stamps Palette.