Code

PrintDocumentImageableArea ia = null;
XpsDocumentWriter w = PrintQueue.CreateXpsDocumentWriter(ref ia);

if (w != null)
{
	DiagramPaginator dp = (DiagramPaginator)diag.DocumentPaginator;
	dp.PageSize = new Size(width, height);
	w.Write(dp);
}
 

Code

MemoryStream ms = new MemoryStream();
Package pkg = Package.Open(ms, FileMode.Create, FileAccess.ReadWrite);
string pack = "pack://temp.xps";
var uri = new Uri(pack);
PackageStore.AddPackage(uri, pkg);
XpsDocument doc = new XpsDocument(pkg, CompressionOption.NotCompressed, pack);
XpsSerializationManager rsm = new XpsSerializationManager(new XpsPackagingPolicy(doc), false);
rsm.SaveAsXaml(dp);
var w = new Window();
DocumentViewer dv = new DocumentViewer();
dv.Document = doc.GetFixedDocumentSequence();
w.Content = dv;
w.Title = windowTitle;
w.ShowDialog();
PackageStore.RemovePackage(uri);