If you don't want people to print your emails - or at least the attachments that you include - there's an easier way than including a line in your signature about thinking twice. Now, you can save an attachment as a WWF file and the recipient won't be able to print it. So named for the World Wildlife Fund, the WWF file format cannot be printed. It's that simple. So, when you send over a memo to be read or a file you want someone to look at - but not print - just save it as a WWF (with this free software).