Thanks for your answer, but it's not an option, as we run a simple tomcat web app.
Currently I'm using your API-access to canvas.toDataURL() feed the base64 result into a hidden form field and post it to the server, which then takes the field, decodes base64, converts the png to PDF, combines it with two overlay PDF's (one dynamic with captions and some text, the other static logo and footer) and return the whole thing as response to the post. The PDF is in total 150 kB, so small enough, it's fast, efficient and easily customizable for us. Resolution of the canvas images is not crisp but ok for print.
To improve the output quality I'd like to do the same thing with the client side jqChart-PDF $('#jqChart').jqChart('exportToPdf') instead of the rasterized canvas image. If you can send the PDF through the browser to the user, you must be able to encode it to base64 and return it by some js function call, or?