It looks like a useful service but in case you didn't know: you can do this locally on macOS using Preview. Click on Tools->Annotate->Signature and add your own

It looks like a useful service but in case you didn't know: you can do this locally on macOS using Preview. Click on Tools->Annotate->Signature and add your own signature. You can even write it down on paper, put in front of webcam and it will recognise it and turn it to black & white. Very useful for filling out different forms.