Force browser to download a pdf file.

pdf-download.php

<?php
if(!isset($_GET['f'])) die('You must specify which files to download');

$f = $_GET['f'];
if(!endsWith($f, '.pdf')) die('File MUST have .pdf extension (' . $f . ')');

$f_array = explode('/', $f);
$file_name = $f_array[count($f_array) - 1];
$file_url = $f;
header('Content-Type: application/octet-stream');
header("Content-Transfer-Encoding: Binary"); 
header("Content-disposition: attachment; filename=\"".$file_name."\""); 
readfile($file_url);


//http://stackoverflow.com/a/10473026/181295
function endsWith($haystack, $needle)
{
    return $needle === "" || substr($haystack, -strlen($needle)) === $needle;
}