RadPdfViewer cannot be used to edit PDF files for now. It was only introduced in 2011 Q3 and we are still working on improving the quality of the text rendering, the import of images, etc.
We do plan to add a selection tool and an option to copy parts of the document and some basic editing capabilities such as highlight and underline, but we will probably commence work on these features for Q2 or Q3 2012.
All the best,
the Telerik team
Explore the entire Telerik portfolio by downloading the Ultimate Collection trial package. Get it now >>