Cari Tanda Tangan Digital dalam File RTF

using (Signature signature = new Signature("signed.pdf"))
{
    DigitalSearchOptions options = new DigitalSearchOptions()
    {
        // tentukan kriteria pencarian khusus
        Comments = "Test comment",
        // kriteria masalah sertifikat
        IssuerName = "John",
        // subjek sertifikat digital
        SubjectName = "Test",
        // tentukan rentang tanggal periode tanda tangan
        SignDateTimeFrom = DateTime.Now.AddMonths(-1),
        SignDateTimeTo = DateTime.Now,
        //
    };
    // mencari tanda tangan di dokumen
    List signatures = signature.Search(options);
    Console.WriteLine("\nSource document contains following signatures.");
    foreach (var digitalSignature in signatures)
    {
        Console.WriteLine("Digital signature found from {0} with validation flag {1}. Certificate SN {2}",
            digitalSignature.SignTime, digitalSignature.IsValid, digitalSignature.Certificate?.SerialNumber);
    }
}