So, why not use \includepdf{the printed, signed and scanned page} in the .tex file? You can do \ifdefined to have it generate both the initial draft for signing

So, why not use \includepdf{the printed, signed and scanned page} in the .tex file? You can do \ifdefined to have it generate both the initial draft for signing and then second iteration with the scanned page. This should preserve document metadata as far as I can tell.