The file is being displayed fine; however, I would like to add some HTML controls above the file when it streams. Is that possible in MVC?
This is not possible in any browser based application. The browser can either download a file or refresh the page with HTML not both. As YijingSun-MSFT suggested, return a View. The View contains a simple JavaScript application to download the file.
https://stackoverflow.com/questions/3749231/download-file-using-javascript-jquery