The origin of the problem might be in the way the PDF converter handles HttpHandlers -- the chart image is served by an HttpHandler and if the converter does not support this, the image might not appear in the PDF document.
Still, RadChart exposes a Save
method allowing you to export the chart to an image on the server. You can use this method and create a separate image file and use this image in the page instead of the chart control. This will allow you to export the page to PDF.
the Telerik team