AaronBowie

define('ePDQ_custom_product_data',TRUE);

add_action('ePDQ_custom_product_data', 'my_ePDQ_custom_product_data');
function my_ePDQ_custom_product_data( $order ) {

  $order_id = $order->get_id(); //558;

  return $order_id;

}

AaronBowie

define('ePDQ_custom_order_id',TRUE);

add_action('ePDQ_custom_order_id', 'my_ePDQ_custom_order_id'); 
function my_ePDQ_custom_order_id( $order ) {

  $invoice_number= $order->get_id(); // invoice number

  return $invoice_number;

}

AaronBowie

add_filter('ag_custom_invoice', 'custom_invoice');

function custom_invoice($id){

  return $id .'some invoice data';

}

AaronBowie

add_filter('ag_custom_po_number', 'custom_po_number');

function custom_po_number($id){

  return $id .'some data';

}