Add Content to WooCommerce Product Description

If you want to add content to WooCommerce product descriptions site-wide, use the following code. Add it to your theme’s functions.php file and change the text on line 5 as desired. Note that this code adds the information at the end of the product description content.

function change_woocommerce_description( $content ) {
    // Only for single product pages in woocommerce
    if ( is_product() ) {
        // The custom content to add
        $custom_content = '<p class="custom-content">' . __("This is the last line in the description", "woocommerce").'</p>';
        // Inserting the custom content at the end of the current product description
        $content .= $custom_content;
    }
    return $content;
}
add_filter( 'the_content', 'change_woocommerce_description' );

More on changing and adding fields to WooCommerce products in the post How to add custom fields to the WooCommerce product page.