Help- Signature button not appearing in annotation toolbar in Preview (Lion)

Hello, new here.

I have just upgraded to Lion, and I was trying to use the new signature feature in Preview.
However, the touted feature does not seem to want to appear (see attached pic) in the annotations toolbar as described in various tutorials on using it.

Does anyone have ideas on why it is missing or what I can do to use the feature other than the old fashioned way of inserting a digital signature?

Thanks,
John

Signatures only works in PDFs, do a Save As...

Thanks a bunch!