Hello. Just figured this one out yesterday. In your apps\#\widgets\Print\templates\Print file, you can modify the code around line 40 (?... my lines are a bit off, due to the poking).
I've been unable to post due to an error message "Your post has been changed because invalid HTML was found in the message body. The invalid HTML has been removed. Please review the message and submit the message when you are satisfied."
I added the readonly ='true' because I don't want my end users to be able to change it. You can leave it off if you want it to be a real option for 'em.
I feel like I was helped in the forums somewhere. It was probably a response from Robert Scheitlin
Look at the changes to the two visible inputs of type="radio" in image above.