FFCore is able to preserve the "green check" for the digital signature, when the PDF is routed to a Save node. If any content is added (e.g., by the Watermark node) to digital signature verification will fail. When the file is submitted to a Fiery, the "green check" is replaced by a "yellow question mark". Whether the submission is through FFCore or Acrobat, the issue remains.
There may be a way on the Fiery to "confirm" the signature. I recommend contacting Xerox support for your printer to determine if this is possible. If you obtain a method to do this, could you please post this?
I am using the trial version of FreeFlow Core, with Xerox 550 with external Fiery.
When I use optiomise node in Core with pdf flattening settings, the digital signature is not getting printed.
I am attaching 2 samples, Original.pdf is with digital signature in green tick mark. second file where digital signature is a question mark.