License for exporting crystal reports to PDF on a server

Hi,

We have developed a desktop application using adobe flex (apache flex). We have purchased a copy of Crystal Reports 11 and have developed several reports (sales receipt, invoice, etc.) using it. We can not embed Crystal Report Viewer in the desktop application as there is no way to do it. So we export the reports to PDF on a server using the .Net code (CR Run-time for Dot net) and then open the PDF in the web browser. We are looking to implement this solution at several client installations. What type of license do we need to buy?
Note:- The solution will be fully deployed at client premises. i.e. the client owns database & API server,