greanmurk

Found a ways myself. First is adding code in theme functions.php:

function my_add_post_type_to_search( $query ) {
	if ( ! is_admin() && $query->is_main_query() && $query->is_search ) {
		$query->set('post_type', array('page', 'post', 'bfd_download') );
	}
}
add_filter( 'pre_get_posts', 'my_add_post_type_to_search' );

Second is just changing “exclude_from_search” to false in the class-better-file-download-admin.php.

Anyway, probably it’s worth to add an option to enable or disable files appearing in search results.