print preview in wpf with telerik document in rich text box

telerik rich text box doesnot support print preview,so im trying to implement print preview but im getting the follwing error

Cannot implicitly convert type 'Telerik.Windows.Documents.Model.Rad开发者_高级运维Document' to 'System.Drawing.Printing.PrintDocument'

So how can i convert this or how can i achieve this one......

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Here is a good example from the official website.

For further help, I think you should post this question in the teleric forums itself.