If you have a scanner, sign a piece of paper, scan the signature and turn it into a JPEG. Each time you want to use a signature just insert the JPEG image into your document.
I always think that an auto-created signature is something of a cop out though and gives a "don't care" impression to the recipient. OK, if you have a thousand to do but for just a few, a handwritten signature gives a much better impression.
I sign about 50 - 75 documents a day and they are all hand done. It would have to be a lot more before I considered a printed signature.
Thanks for your responses. I did consider the option of scanning my signature. It comes out a different size. Also, in pursuit of a paperless office, I wondered if I could sign and then archive the document as a pdf file using Open Office (File - Export as pdf).