EDD: Change Add-to-Cart Button Text

<?php
add_filter( 'edd_add_to_cart_label', 'scseed_edd_custom_cart_label' );
function scseed_edd_custom_cart_label( $label ) {
    if ( ! class_exists( 'Easy_Digital_Downloads' ) ) {
        return $label;
    }
    // Change to any text you prefer.
    return __( 'Buy Now', 'scseed' );
}