[samaparicio]

Just to point out that when you send a PDF document signed with Preview, I can open that document, extract your signature, and paste it in any other PDF that I want to. For me, this makes it too dangerous to use.

[beering]

As opposed to regular docs, where I can photograph/scan/screenshot your signature and paste it in?

[jsmeaton]

Couldn't they just scan/cut/paste a regularly signed signature? I know it makes the process harder - but someone determined..

[joenathan]

Or just screenshot it.

[EwanToo]

Unlike say a photocopier and a pair of scissors, or cutting a pasting a screenshot of a scanned document?

It's always been trivial to forge a signature to pass cursory examination, this is just another easy way.

[js2]

The PDF can be flattened by printing, then saving from the print dialog.