namespace _666
{
    class Program
    {
        static void Main(string[] args)
        {
            PdfReader reader = null;
            reader = new PdfReader("C:\\DISTRIB\\1.pdf");

           // Получаем подписи из документа
            AcroFields af = reader.AcroFields;

            List<string> names = af.GetSignatureNames();
            foreach (string name in names)
            {

                string message = "Signature name: " + name;
                message += "\nSignature covers whole document: " + af.SignatureCoversWholeDocument(name);
                message += "\nDocument revision: " + af.GetRevision(name) + " of " + af.TotalRevisions;

                

                // Проверяем подпись
                PdfDictionary singleSignature = af.GetSignatureDictionary(name);
                //PdfString asString1 = singleSignature.GetAsString(PdfName.CONTENTS);

                /////////////////////
                //Указываю LOCATION//
                ////////////////////
                PdfString asString1 = singleSignature.GetAsString(PdfName.LOCATION);

                //далее все в точности как по примеру

                byte[] signatureBytes = asString1.GetOriginalBytes();

                RandomAccessFileOrArray safeFile = reader.SafeFile;

                PdfArray asArray = singleSignature.GetAsArray(PdfName.BYTERANGE);
                using (
                    Stream stream =
                        (Stream)
                        new RASInputStream(
                            new RandomAccessSourceFactory().CreateRanged(
                                safeFile.CreateSourceView(),
                                (IList<long>)asArray.AsLongArray())))
                {
                    using (MemoryStream ms = new MemoryStream((int)stream.Length))
                    {
                        stream.CopyTo(ms);
                        byte[] data = ms.GetBuffer();

                        // Создаем объект ContentInfo по сообщению.
                        // Это необходимо для создания объекта SignedCms.
                        ContentInfo contentInfo = new ContentInfo(data);

                        // Создаем SignedCms для декодирования и проверки.
                        SignedCms signedCms = new SignedCms(contentInfo, true);

                        // Декодируем подпись
                        signedCms.Decode(signatureBytes);

                        bool checkResult;

                        try
                        {
                            signedCms.CheckSignature(true);
                            checkResult = true;
                        }
                        catch (Exception)
                        {
                            checkResult = false;
                        }

                        message += "\nDocument modified: " + !checkResult;

                        foreach (var sinerInfo in signedCms.SignerInfos)
                        {
                            message += "\nCertificate " + sinerInfo.Certificate;
                            X509Certificate2 cert = signedCms.Certificates[0];
                            var isCapiValid = cert.Verify();
                            message += "\nCAPI Validation: " + isCapiValid.ToString();


                            foreach (var attribute in sinerInfo.SignedAttributes)
                            {
                                if (attribute.Oid.Value == "1.2.840.113549.1.9.5")
                                {
                                    Pkcs9SigningTime signingTime = attribute.Values[0] as Pkcs9SigningTime;
                                    message += "\nDate: " + signingTime.SigningTime;
                                }
                            }
                            message += "\n\n";
                        }
                        
                        Console.WriteLine(message);
                        Console.ReadKey();
                    }
                }
            }
        }
    }
}