Prevent hotlinking requests by mime

I am trying to prevent people hotlinking to PDF AND DOC files. Usually, i would approach this with a .htaccess rule like this:

RewriteEngine On
RewriteBase /
RewriteCond %{HTTP_REFERER} !^$
RewriteCond %{HTTP_REFERER} !^http://(www\.)?domain.com/.*$ [NC]
RewriteRule \.(pdf|doc)$ /home/ [R=302,L]

However, many of these files are linked to through php scripts like filedownload.php?id=5 which then trigger the download of a PDF/DOC file. Is there a way to prevent hotlinking to these files via the mime of the outputted file? another way?

edit - added this source to show how files are called:

header("Pragma: public"); 
header("Expires: 0");
header("Cache-Control: must-revalidate, post-check=0, pre-check=0");
header("Cache-Control: private",false);
header("Content-Type: $ctype");
header("Content-Disposition: attachment; filename=\"".basename($fn)."\";" );
header("Content-Transfer-Encoding: binary");
header("Content-Length: ".$fs);
echo $upload["file_contents"];
exit();