Enable revisions on the downloads post type. Note this will be added into core from EDD v2.0
<?php
/*
 * Plugin Name: Easy Digital Downloads - Enable Revisions
 * Description: Enable revisions on the downloads post type. Note this will be added into core from EDD v2.0
 * Author: Easy Digital Downloads
 * Author URI: https://easydigitaldownloads.com/
 * Version: 1.0
 */

function sumobi_edd_modify_edd_download_supports( $supports ) {
	$supports[] = 'revisions';
	return $supports;	
}
add_filter( 'edd_download_supports', 'sumobi_edd_modify_edd_download_supports' );
To implement this snippet on your site, create a brand new, empty WordPress plugin and paste the above code inside.