Thank you Jose!
However, I don’t want to use a child theme, I tried adding a code snippet like the one below but doesn’t work. I think the filter hook is incorrect.
function add_tracking_number_to_pdf_template($template_output, $po) {
$tracking_number = $po->tracking_order_number;
$ tracking_number _html = ‘<div class=”row”>’;
$ tracking_number _html .= ‘<span class=”label”>’ . esc_html__(‘Tracking Number:’, ‘atum-plugin’) . ‘ </span>’;
$ tracking_number _html .= ‘<span class=”field”>’ . esc_html($ tracking _number) . ‘</span>’;
$ tracking_number _html .= ‘</div>’;
$template_output .= $ tracking_number _html;
return $template_output;
}
add_filter(‘atum_purchase_order_pdf_template_output’, ‘ add_tracking_number_to_pdf_template ‘, 10, 2);