I find the solution.
private static void SaveXpsDocument(XpsDocument xpsDocument, string filePath)
{
XpsDocument xpsd = new XpsDocument(filePath, FileAccess.ReadWrite);
System.Windows.Xps.XpsDocumentWriter xw = XpsDocument.CreateXpsDocumentWriter(xpsd);
xw.Write(xpsDocument.GetFixedDocumentSequence());
xpsd.Close();
}