Reader Michael Burke dutifully accepted my counsel but came up with unexpected results. He writes:
I followed your advice in How to Sign Digital Documents for capturing my signature in Preview, but it came out 90 degrees from horizontal. I would like to know why my signature came out vertical, not horizontal, and how to fix that.
I haven't had this problem, but it's not unknown to me. Why? It's a bug. How? Like so:
You could accept that your Mac is mucking things up and instead of holding your signature in front of the camera in the normal way, hold it vertically. Snap the shot and it will come out rotated to the horizontal.
The other option is to export an unsigned copy of the PDF you're working with (in Preview, File > Export), open the copy, and then add the signature. According to those who've done this, the signature appears correctly on the copy even though it didn't with the original.