<?php
//* Do NOT include the opening php tag
function ee_add_custom_messaging_after_attendee_information_registration_checkout_footer() {
?>
<p style="text-align: center; font-weight:bold;">Replace Me</p>
<?php
}
add_action( 'AHEE__SPCO__reg_form_footer', 'ee_add_custom_messaging_after_attendee_information_registration_checkout_footer' );
The example above can be added to your child theme's functions.php file or a site specific plugin (https://eventespresso.com/wiki/create-site-specific-plugin-wordpress-site/). Then change Replace Me to your actual messaging.
References:
https://eventespresso.com/topic/static-text-to-appear-at-very-end-of-registration-form/