Custom Download Templates Filter

gistfile1.php

<?php

/**
 * Allow Custom Post Templates for Downloads (in Easy Digital Downloads)
 **/
function my_cpt_post_types( $post_types ) {
    $post_types[] = 'download';
    return $post_types;
}
add_filter( 'cpt_post_types', 'my_cpt_post_types' );