Hi! I’m not sure what you mean by ‘invoicing_invoice_number_id’, there is no such id in use by our plugin (just to be certain, this forum is for WooCommerce PDF Invoices & Packing Slips).
You can programmatically retrieve the invoice data for a given order/order_id like so:
$order = wc_get_order( $order_id );
$invoice = wcpdf_get_document( 'invoice', $order );
if ( $invoice && $invoice->exists() ) {
$invoice_number = $invoice->get_number(); // this retrieves the number object with all the data related to the number
$invoice_number_formatted = $invoice_number->get_formatted();
$invoice_number_plain = $invoice_number->get_plain();
}
The formatted invoice number is also stored in the order meta as _wcpdf_invoice_number
(which may be quicker/more convenient if that’s good enough for your purposes too).
Hope that helps!