Notes to Invoice and Packing slip named Serial number

Hi @hypostatic,

If you only want to customize that unique string, I think the best way to achieve it is using this code snippet:

 * PDF Invoices & Packing Slips for WooCommerce:
 * Customize labels on the PDF documents
add_filter( 'wpo_wcpdf_html_filters', function( $filters ) {
	$filters[] = array( 'gettext', 'wpo_wcpdf_customize_string_translation', 999, 3 );
	return $filters;
}, 10, 1 );
function wpo_wcpdf_customize_string_translation( $translation, $text, $domain ) {
	if ( $domain == 'woocommerce-pdf-invoices-packing-slips' ) {
		switch ( $text ) {
			// Repeat as many cases as strings you want to translate
			case 'Notes':
				$translation = 'Serial Number';
	return $translation;

I recommend using the code snippet above to translate only a few of strings, but for more than 10 strings, it’s better using a plugin like Loco Translate.


This site will teach you how to build a WordPress website for beginners. We will cover everything from installing WordPress to adding pages, posts, and images to your site. You will learn how to customize your site with themes and plugins, as well as how to market your site online.

Buy WordPress Transfer