wc-wpo-wcpdf-billing-address-company-vat-simple.php

<?php
add_action( 'wpo_wcpdf_billing_address', function ( $billing_address, $invoice ) {
	if ( ! empty( $invoice ) ) {
		$billing_address_prefix = '';

		// billing_company
		$company_name = trim( $invoice->order->get_meta( '_billing_company', true, 'view' ) );
		if ( ! empty( $company_name ) ) {
			$billing_address_prefix .= "<b>$company_name</b><br>";
		}

		$company_vat = trim( $invoice->order->get_meta( '_billing_wooccm11', true, 'view' ) );
		if ( ! empty( $company_vat ) ) {
			$billing_address_prefix .= "<b>PIVA: $company_vat</b><br>";
		}

		if ( ! empty( $billing_address_prefix ) ) {
			$billing_address = $billing_address_prefix . '<hr>' . $billing_address;

		}
	}

	return $billing_address;
}, 10, 2 );