test.cs

using TXTextControl;

SaveSettings saveSettings = new SaveSettings();

var metaData = File.ReadAllText("metadata.xml");

// byte array from the ZUGFeRD XML file
var zugferdXML = File.ReadAllBytes("rechnung_206_4267_zugferdaddon.xml");

// create a new embedded file
var zugferdInvoice = new EmbeddedFile(
  "ZUGFeRD-invoice.xml",
  zugferdXML,
  metaData);

zugferdInvoice.Description = "ZUGFeRD-invoice";
zugferdInvoice.Relationship = "Alternative";
zugferdInvoice.MIMEType = "application/xml";
zugferdInvoice.LastModificationDate = DateTime.Now;

// set the embedded files
saveSettings.EmbeddedFiles = new EmbeddedFile[] { zugferdInvoice };

using (ServerTextControl tx = new ServerTextControl())
{
	tx.Create();

	tx.Text = "Invoice";

	// export the PDF
	tx.Save("invoice.pdf", StreamType.AdobePDFA, saveSettings);
}