The issue is rather unfortunate but comes directly from the Silverlight framework, so there aren't many viable solutions.
Basically, in Silverlight applications silent printing is only available when running the app with elevated trust (out-of-browser). Otherwise, the PrintDialog needs to be shown and all dialogs in Silverlight can only be in result of a user action, thus the security exceptions you are seeing.
One possible solution would be to find a way to print from the web application
. You could send the RadDocument in HTML format to the server and print it from there. The recommended approaches for doing this I found online, however, seem to include showing the print dialog too.
Another option, if applicable for you, is to merge all documents in a single one. This will allow to only show the dialog to the end users once and avoid the constant prompts. If this sounds reasonable to you, take a look at the MergeDocuments SDK example
to see how you can merge several RadDocument instances into one.
I hope this is useful.
Do you want to have your say when we set our development plans? Do you want to know when a feature you care about is added or when a bug fixed? Explore the Telerik Feedback Portal
and vote to affect the priority of the items