It is trivially recognizable in PDF viewers like Adobe Reader that a signature image was pasted in (the image rectangle around the signature highlights), and can therefore be rejected as not being a genuine signature, unless you turn the whole page into an image to make it look like a scan.

Make a very high-quality noise-free image of your signature, with a transparent background. Drop it onto an equally high-quality PDF and skew it a bit. Add some toner noise to the whole image and skew the image a small bit.

I think you can make it look decent. Haven't tried it though.