PDF Signatures
patio11: The obvious choice is one of the various Adobe tools.If you're feeling in a not-spend-money mood, you can do it with ImageMagick.http://www.imagemagick.org/Usage/annotating/Writing the command lines for it takes some getting used to, but after you do it you can do some VERY fun things with ImageMagick.  I'm using it to do a lot of automated conversion/cropping/etc for the next version of my app.convert some.pdf some.gifIt is really magic.