Change the “Add to Cart” text on the single product page, conditionally

functions.php

<?php
add_filter( 'woocommerce_product_single_add_to_cart_text', 'change_add_to_cart_text', 10, 2 );
function change_add_to_cart_text( $default, $product ) {
    $terms = get_the_terms( $product->id, 'product_cat' );

    foreach ( $terms as $term ) {
        if ( $term->name == 'Posters' ) {
            $default = __( 'Custom Text', 'domain' );
            break;
        }
    }

    return $default;
}