creating an XPS Document from a FlowDocument and attach it on the fly

问题

I have a FlowDocument that I want to convert to an XPS Document and attach it to an e-mail and send it all together. I'm using this code

 public static MemoryStream FlowDocumentToXPS(FlowDocument flowDocument, int width, int height)
    {
        MemoryStream stream = new MemoryStream();
        using (Package package = Package.Open(stream, FileMode.Create, FileAccess.ReadWrite))
        {
            using (XpsDocument xpsDoc = new XpsDocument(package, CompressionOption.Maximum))
            {                  
                XpsSerializationManager rsm = new XpsSerializationManager(new XpsPackagingPolicy(xpsDoc), false);
                DocumentPaginator paginator = ((IDocumentPaginatorSource)flowDocument).DocumentPaginator;
                paginator.PageSize = new System.Windows.Size(width, height);
                rsm.SaveAsXaml(paginator);
                rsm.Commit();                
            }
        }
        stream.Position = 0;
        Console.WriteLine(stream.Length);
        Console.WriteLine(stream.Position);
        return stream;   
    }

Then I attach it using this code:

Attachment xps = new Attachment(FlowDocumentToXPS(FD, 768, 676), "FileName.xps", "application/vnd.ms-xpsdocument");

where FD is the FlowDocument I want to convert , I'm receiving 0.0KB size XPS file attached and it can't be open with the XPS Viewer , what I'm missing here ?

EDIT: The final code that worked , see the comments

Thanks in advance