If you want to recreate this particular message, simply type the words into your signature using your mail preferences (or whatever message you’d like). The little tree icon is a capital “P” within the Webdings font. It may not be the most ideal icon for this message, but its found on most computers, be they Mac or PC.
Do you really need to print that email? In most cases, no. And in most cases we don’t print our emails, but I’ve known some people who have a very old-school style when it comes to dealing with email (print, read, reply). A friendly reminder might just save a little more paper and encourage some to think twice about other documents that may not need to be printed. I’ve already added it to my signature.