Add custom text just before the "Purchase" button at checkout
<?php
/*
 * Plugin Name: Easy Digital Downloads - Add Custom Text Before Purchase Button
 * Description: Add custom text just before the "Purchase" button at checkout
 * Author: Easy Digital Downloads
 * Author URI: https://easydigitaldownloads.com/
 * Version: 1.0
 */

function sumobi_edd_purchase_form_before_submit() { ?>
	<p>Your custom text</p>
<?php }
add_action( 'edd_purchase_form_before_submit', 'sumobi_edd_purchase_form_before_submit', 1000 );
To implement this snippet on your site, create a brand new, empty WordPress plugin and paste the above code inside.