I wish Preview had a better way to import signatures. I was messing around one day and made one I really liked with Apple Notes on the iPad. It looks like I eventually got it in Preview, but it doesn't look as clean as it did in Notes.

I think I ended up printing it out and holding it up to my webcam, but it wasn't easy. I remember fighting with it a fair bit and I'm still not happy with the results. You'd think Apple Notes and Preview would be able to talk to each other enough to import directly.