When you use the FastReport .Net together ASP.Net MVC framework you have easy method for creating file in any supported format on button press in HTML form.

Add next code in View:

 @using (Html.BeginForm("GetFile", "Home"))
 {
         <input id="pdf" type="submit" value="Export to PDF" />
 }

GetFile - name of controller handler, Home - name of controller (HomeController.cs for example)

Add name space in controller: more...