There is a way you can keep you signature stored within the Preview application on your mac. This can be very handy if you ever need to be able to electronically sign documents.
To get to this Load Preview, then go to Preferences-> Signatures. Once you have this loaded Click "Create Signature".
Once this has loaded your camera will be active, and there will be a blue line across the camera screen, sign your signature onto a plain piece of paper using a thin marker pen, something like a Sharpie (this just helps it stand out). Once you have your signature hold it close enough so that it fits into the box on the right and is on the blue line.
Once you have you signature ready to go then click on Accept. Then when you look in Preferences you can see your signatures.
To insert them into a PDF, you can either use the Edit tool bar and select Signatures.
Or you can you can go to the Tools menu->Annotate->Signature. Then you just resize your box to how big you want the signature and drop it on the document.
I am always interested in your thoughts so if you have any comments or feedback then please feel free to add any comments, or you can mail me here