mypmpro-adjust-shipping-text.php

<?php
/**
 * This recipe will adjust shipping related text to something of your preference.
 *
 * You can add this recipe to your site by creating a custom plugin
 * or using the Code Snippets plugin available for free in the WordPress repository.
 * Read this companion article for step-by-step directions on either method.
 * https://www.paidmembershipspro.com/create-a-plugin-for-pmpro-customizations/
 */

function changet_text_shipping_information( $translated_text, $text, $domain ) {  
    switch ( $translated_text ) {
         case 'Shipping Address' :
            $translated_text = __( 'Postal Address', 'paid-memberships-pro' );
            break;
        case 'Ship to the billing address used above.' :
            $translated_text = __( 'Ship to the billing address.', 'pmpro-shipping' );
            break;
    }

    return $translated_text;
}
add_filter( 'gettext', 'changet_text_shipping_information', 20, 3 );