PHP-MYSQL

Make a link to this PHP page when DOWNLOAD button is clicked.

For PDF:-
If you want the user to be prompted to save the data you are sending, such as a generated PDF file, you can use the Content-Disposition header to supply a recommended filename and force the browser to display the save dialog.

<?php

if(VALID_USER) {

switch( $ext ){
   case "pdf": $ctype="application/pdf";              break;
   case "exe": $ctype="application/octet-stream";      break;
   case "zip": $ctype="application/zip";              break;
   case "doc": $ctype="application/msword";            break;
   case "xls": $ctype="application/vnd.ms-excel";      break;
   case "ppt": $ctype="application/vnd.ms-powerpoint"; break;
   case "gif": $ctype="image/gif";                    break;
   case "png": $ctype="image/png";                    break;
   case "jpg": $ctype="image/jpg";                    break;
   default:    $ctype="application/force-download";
}

header('Content-type: $ctype');

header('Content-Disposition: attachment; filename="downloaded.' . $ext . '"' );

readfile('original.pdf');

}
else {
 echo "Invalid user";
 exit();
}
?>

For more, read:-
http://www.php.net/manual/en/function.header.php

replace the filenames accordingly instead of PDF.

I just realised my code was incomplete!

you should add the following for managing the download:

   $download_size = strlen($dataStream);
   header("pragma: public");
   header("expires: 0");
   header("Cache-Control: private");
   header("Content-type: application/octet-stream");
   header("Content-Disposition: attachment; filename=$fileDownload");
   header("Accept-Ranges: bytes");
   header("Content-Length: $download_size");
                     
   echo $dataStream;