How to make PDF file downloadable in HTML link?

<a href="pdf_server.php?file=pdffilename">Download my eBook</a>

header("Content-Type: application/octet-stream");

$file = $_GET["file"] .".pdf";
header("Content-Disposition: attachment; filename=" . urlencode($file));
header("Content-Type: application/force-download");
header("Content-Type: application/octet-stream");
header("Content-Type: application/download");
header("Content-Description: File Transfer");
header("Content-Length: " . filesize($file));
flush(); // this doesn't really matter.
$fp = fopen($file, "r");
while (!feof($fp))
{
    echo fread($fp, 65536);
    flush(); // this is essential for large downloads
}
fclose($fp);

header("Content-Type: application/octet-stream");

def index

 respond_to do |format|
   format.html # Your HTML view
   format.pdf { render :layout => false }
 end
end