Thanks for contacting us with this issue.
We investigated it and it looks like the problem is in the way RadPdfViewer shows the file, as when you try to open the saved to disk PDF file in our online demo
, the results are the same as when passing a stream to a viewer as in your setup. The good news is that we tried opening such file in our development version and it seems to work as expected. Our next official release - Q1 2013, is expected in the of February and should solve the problem you are observing.
Let us know if there is anything else we can help you with!
All the best,