dani-snippets

add_action( 'before_delete_post', 'delete_attached_media_pdf' );
function delete_attached_media_pdf( $post_id ) {
  if( get_post_type($post_id) == "type-your-custom-post-type-name-here" ) {
    $attachments = get_attached_media( 'application/pdf', $post_id );
    foreach ($attachments as $attachment) {
      wp_delete_attachment( $attachment->ID, 'true' );
    }
  }
}