Editing XPS document

//create a flow document
Paragraph paragraph = new Paragraph();
paragraph.Inlines.Add("This is a bit of text");
FlowDocument document1 = new FlowDocument(paragraph);

//create another flow document
Paragraph paragraph2 = new Paragraph();
paragraph2.Inlines.Add("this is another one!");
FlowDocument document2 = new FlowDocument(paragraph2);

// append document2 to document1
for (int i = 0; i < document2.Blocks.Count; i++)
{
    document1.Blocks.Add(document2.Blocks.ElementAt(i));
}

//save to xps
XpsDocument xpsDocument = new XpsDocument(@"C:\temp\test.xps", FileAccess.ReadWrite);
XpsSerializationManager xpsSerializationManager = new XpsSerializationManager(new XpsPackagingPolicy(xpsDocument), false);
DocumentPaginator documentPaginator = ((IDocumentPaginatorSource)document1).DocumentPaginator;
xpsSerializationManager.SaveAsXaml(documentPaginator);
xpsDocument.Close();