Use this if you want to upload a PDF to the WordPress media library but restrict access so that only visitors referred from a specific external page can view or download it.

Steps:

 

Upload the PDF to a protected folder (not directly in /wp-content/uploads/).

Create a PHP script (pdf-proxy.php) in your theme or child theme folder:

<?php
// www.websitefunctions.com
$allowed_referer = 'https://trusted-website.com'; // change it to the url of the referrer website
if (!isset($_SERVER['HTTP_REFERER']) || strpos($_SERVER['HTTP_REFERER'], $allowed_referer) === false) {
    header("HTTP/1.1 403 Forbidden");
    die("Access denied");
}
 
$file = 'path-to-your-pdf.pdf'; // Change to your PDF file path
header('Content-Type: application/pdf');
header('Content-Disposition: inline; filename="' . basename($file) . '"');
readfile($file);
exit;

Link to the PHP file instead of the direct PDF URL.