data.cs

static void Main(string[] args)
{
    if (args == null || args.Length < 2) return;

    // get read and write pipe handles
    // roles are reversed from how the other process is passing the handles
    string pipeWriteHandle = args[0];
    string pipeReadHandle = args[1];

    // create 2 anonymous pipes for duplex communications
    using (var pipeRead = new AnonymousPipeClientStream(PipeDirection.In, pipeReadHandle))
    using (var pipeWrite = new AnonymousPipeClientStream(PipeDirection.Out, pipeWriteHandle))
    {
        try
        {
            var lsValues = new List<string>();

            // get message from hosting process
            using (var sr = new StreamReader(pipeRead))
            {
                string sTempMessage;

                // wait for "sync message" from the other process
                do
                {
                    sTempMessage = sr.ReadLine();
                } while (sTempMessage == null || !sTempMessage.StartsWith("SYNC"));

                // read until "end message" from the server
                while ((sTempMessage = sr.ReadLine()) != null && !sTempMessage.StartsWith("END"))
                {
                    lsValues.Add(sTempMessage);
                }
            }

            // send value to calling process
            using (var sw = new StreamWriter(pipeWrite))
            {
                sw.AutoFlush = true;
                // send a "sync message" and wait
                sw.WriteLine("SYNC");
                pipeWrite.WaitForPipeDrain(); // wait here

                PassingObject dataObject = 
                  JsonConvert.DeserializeObject<PassingObject>(lsValues[0]);
                ReturningObject returnObject = new ReturningObject();

                try
                {
                    // create a new ServerTextControl for the document processing
                    using (TXTextControl.ServerTextControl tx =
                      new TXTextControl.ServerTextControl())
                    {
                        tx.Create();
                        tx.Load(dataObject.Document, 
                          TXTextControl.BinaryStreamType.InternalUnicodeFormat);

                        using (MailMerge mailMerge = new MailMerge())
                        {
                            mailMerge.TextComponent = tx;
                            mailMerge.MergeJsonData(dataObject.Data.ToString());
                        }

                        byte[] data;
                        tx.Save(out data, TXTextControl.BinaryStreamType.AdobePDF);

                        returnObject.Document = data;
                    }

                    sw.WriteLine(JsonConvert.SerializeObject(returnObject));
                    sw.WriteLine("END");
                }
                catch (Exception exc)
                {
                    returnObject.Error = exc.Message;

                    sw.WriteLine(JsonConvert.SerializeObject(returnObject));
                    sw.WriteLine("END");
                }
            }
        }
        catch
        {

        }
    }
}