WWF is a new, green file format, that can’t be printed out.
It was developed as initiative to save trees and Discourage unnecessary printout of PDF files.Read more about WWF Format So,If you are sure for documents that dont need printing out,save them as WWF file and join “Save Trees” Campaign.
The Software is free to download for Windows Systems/Mac Systems and use it ,to save the file in wwf format. A WWF format file,can be read in any of the PDF readers ,but cant be printed. External User wont be even able to find the difference of file ,if wwf format is renamed to pdf format since ,every option seems to be the same except the printing option. Think Green and support the new campaign to save trees