Hi Scott,
Thank you for contacting Telerik Support.
Telerik Reporting is a reporting solution and part of its capabilities are exporting to various formats. Our product is not a PDF Reader/Writer application. Combining two PDF files is much more complex than concatenating two byte arrays, so you will need a software that specializes in that. There are a plenty of such products on the web -- both commercial and open-source, so I would suggest researching them to see which one will best suite your needs.
Do not hesitate to contact us if you have any other questions.
Best wishes,
Ross
the Telerik team