test.cs

using System.Data;
using System.Text;
using TXTextControl.DocumentServer;

string xmlData = File.ReadAllText("data.xml");

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

    MailMerge mailMerge = new MailMerge();
    mailMerge.TextComponent = tx;

    // dataset from XML
    DataSet ds = new DataSet();
    ds.ReadXml(new MemoryStream(Encoding.UTF8.GetBytes(xmlData)));

    // merge data
    mailMerge.Merge(ds.Tables["SupplyChainTradeTransaction"]);

    // save as PDF
    tx.Save("output.pdf", TXTextControl.StreamType.AdobePDF);
}