Please verify that you have all required assembly references. Text not showing is usually due to a missing Telerik.Windows.Zip.dll, which is required by RadPdfViewer to show a file. In a nutshell, all required dlls by the control are:
For the toolbar, you'd also need:
If this is not the cause of the problem, we would appreciate a little more information about the version of the controls you are using, the Silverlight version, OS, printer, etc.
the Telerik team
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