Hello Chris!
You can absolutely sign a PDF more than once in 13. When you're in PDF Signing mode, you can do everything with Signatures on a PDF that you can do on an image in Unity 13, including applying multiple signatures. I don't have the answer to your second question, but I've contacted someone on the demo team and hopefully I'll have that information for you shortly. As for signing multiple documents, this is not possible right now. As applying a signature is a visual addition to the document, the document must be visible for it to be placed.
If you're looking for an expedient way to apply a signature to a document, I would recommend first setting up a Stored User Signature for the user who will be doing the signing, and then to configure the Signature Location in question to use Stored Signatures if available and autosave. If you want to save one more click, make sure the User Option "Show my stored signature before applying it to documents." is disabled. Hope this helps!
