BullZip PDF Printer by BioPDFBullZip is another PDF tool that works as a virtual print driver and uses Ghostscript to convert documents. Like Doro, it also allows you to convert printable document or image to PDF format but on top of that, it also lets you add watermarks, merge PDF files and even add protection to your PDF files. It is free for up to 10 users and offers installation of promotional, third party components. You may check the guidelines here.