The RadPdfViewer throws ArgumentOutOfRangeException, when document is loaded. Resolution: An exception message is shown when load the pdf document which contains unsupported encryption method.
Let me also add a link to the feature request for the Encryption Algorithm 4 support: http://feedback.telerik.com/Project/154/Feedback/Details/153358-add-radpdfviewer-add-support-for-encryption-algorithm-4