Hi,
You can return the result as a download easily by setting this property to true:
http://www.essentialobjects.com/doc/eo.pdf.mvc.mvctopdf.resultasdownload.aspxThe tricky part is this would replace the contents in the current window with the PDF file by default. This is because HTTP works strictly by request/response pairs. Your browser sends a request to the server, gets a response and loads that response. That response can either be an HTML page (the same page that contains your drop down list) or the PDF file. It can not be both.
In order to achieve what you want to achieve, you must use an additional pair of request/response. An very common way to add another pair of request/response in your page is to use an iframe. The iframe can have its own form, post its own data and if your server side code for that iframe returns a download, the browser will prompt you as a download. Since it's an iframe, it is separate from your main contents.
Details about using an iframe to trigger a download is beyond the scope of our support --- it does not have anything to do with our product or even MVC at all. You can search online and you should be able to find plenty of information on this. If you still have any specific questions about our product while implementing this, please feel free to ask.
Thanks!