The PITS issue is for support of encrypted documents in RadPdfViewer and the PDF viewer can indeed show encrypted documents, provided that the standard encryption mechanism is used and there is no password.
When it comes to encrypting documents from RadRichTextBox on export, this feature has not been scheduled. We will log it as a feature request, but at this point it is not clear if and when it will be implemented.
All the best,
the Telerik team