Not sure if you want transparency or you want the stamp cropped. You can open the stamp PDF file in Photoshop, crop the image or make a selection and copy the selection to a new layer. Delete the background and save as a Photoshop PDF file. All the unselected area will be transparent. You'll then need to add the new image to your custom stamps.
ted
The author of numerous books on Acrobat, Photoshop, Illustrator and the Adobe Creative Suite, and an international speaker on Adobe Acrobat, Ted Padova is a well-known PDF guru.
ted
The author of numerous books on Acrobat, Photoshop, Illustrator and the Adobe Creative Suite, and an international speaker on Adobe Acrobat, Ted Padova is a well-known PDF guru.