test.cs

using (TXTextControl.ServerTextControl tx = new TXTextControl.ServerTextControl()) {
   tx.Create();
   tx.Load("invoice-template.tx", TXTextControl.StreamType.InternalUnicodeFormat);

   using (MailMerge mailMerge = new MailMerge()) {
      mailMerge.TextComponent = tx;
      mailMerge.MergeObjects(invoices, false);
   }

   tx.Save("results.pdf", TXTextControl.StreamType.AdobePDF);
}