With Lion you also get a new feature called “Signature Capture”. This means you can sign PDF files by using the build in webcam of your Mac to take a picture of your signature. It’s fairly easy: Take a thick pen (a standard ballpoint pen might be a bit thin) and write your signature on a piece of paper. Open a PDF file in Preview and click on the symbol which looks like a pen to show the “Annotations Toolbar”. Here you will find the signature tool and may choose something like “Create Signature from FaceTime HD camera.” Now hold the paper straight in front of the cam and the tool will capture your signature, mirror it and add it to your PDF document. You can keep that signature for further use. Pretty cool and useful, huh!