using Syncfusion.Pdf.Parsing;
using Syncfusion.Pdf.Security;
using System.Security.Cryptography.X509Certificates;

//Load the PDF document.
using (PdfLoadedDocument loadedDocument = new PdfLoadedDocument(Path.GetFullPath(@"Data/Input.pdf")))
{
    //Gets the signature field.
    PdfLoadedSignatureField signatureField = loadedDocument.Form.Fields[0] as PdfLoadedSignatureField;
    //Validates signature and gets the validation result.
    PdfSignatureValidationResult result = signatureField.ValidateSignature();
    //Gets signer certificates
    PdfSignerCertificate[] certifcate = result.TimeStampInformation.SignerCertificates;
    //Print the certifcate value
    foreach (PdfSignerCertificate signerCertificate in certifcate)
    {
        if (signerCertificate.OcspCertificate != null)
        {
            Console.WriteLine("------------OCSP Certificate-------------");
            Console.WriteLine();
            foreach (X509Certificate2 item in signerCertificate.OcspCertificate.Certificates)
            {
                Console.WriteLine("The OCSP Response was signed by " + item.SubjectName.Name);
            }
            Console.WriteLine("Is Embedded: " + signerCertificate.OcspCertificate.IsEmbedded);
            Console.WriteLine("ValidFrom: " + signerCertificate.OcspCertificate.ValidFrom);
            Console.WriteLine("ValidTo: " + signerCertificate.OcspCertificate.ValidTo);
            Console.WriteLine();
            continue;
        }
        if (signerCertificate.CrlCertificate != null)
        {
            Console.WriteLine("------------CRL Certificate--------------");
            Console.WriteLine();
            foreach (X509Certificate2 item in signerCertificate.CrlCertificate.Certificates)
            {
                if (item != null)
                {
                    Console.WriteLine("The CRL was signed by " + item.SubjectName.Name);
                }
            }
            Console.WriteLine("Is Embedded: " + signerCertificate.CrlCertificate.IsEmbedded);
            Console.WriteLine("ValidFrom: " + signerCertificate.CrlCertificate.ValidFrom);
            Console.WriteLine("ValidTo: " + signerCertificate.CrlCertificate.ValidTo);
            break;
        }
    }
}