The signature is valid, but the document has been. The signature has not yet been validated and the document has not been updated since signed. If you happen to work in a context which technologically got stuck in the early 2000s, and if you indeed are required to enable such (nowadays invalid) behavior, you may consider re-integrating the code for generating those pre-Acrobat6 layers in the current iText 7 sign module. If the signer is known and trusted, see Importing a Trusted Identity Certificate to add the identity to your list of trusted identities.
IText 7.x, being a product started in the 2010s, got rid of this burden. IText(Sharp) 5.x, having inherited its signing API implementation base from iText 2.x/4.x, still offered a backward switch ( PdfSignatureAppearance.Acro6Layers) which set to false allowed the creation of signature appearances supporting those in-document validation status marks.
#PDF SIGNATURE VALIDITY UNKNOWN PDF#
In particular that behavior has never been specified in the ISO PDF specification ISO 32000 on the contrary it has been forbidden in the update ISO 32000-2. What you describe is a behavior that has been deprecated in 2003 when Adobe Acrobat 6 has been published. Why does the digital signatures status show up as UNKNOWN in Adobe. A digital signature is printed on my pdf but not as what I expected, it should show a validity unknown symbol or signature valid symbol but it is not getting printed.