htaccess prevent pdf caching

.htaccess
<FilesMatch ".(pdf)$">
  FileETag None
  <ifModule mod_headers.c>
    Header unset ETag
    Header set Cache-Control "max-age=0, no-cache, no-store, must-revalidate"
    Header set Pragma "no-cache"
    Header set Expires "Wed, 11 Jan 1984 05:00:00 GMT"
  </ifModule>
</FilesMatch>