TOPIC:

If (! Has_filter ('wpo_wcpdf_invoice_number')) {
Add_filter ('wpo_wcpdf_invoice_number', array ($ this, 'format_invoice_number'), 20, 4);
}

// Support for specific plugins:
If (get_option ('customize_invoice', 'no') === 'yes') {  //<< this line
$ This-> thirdparty_wpo_wcpdf_init ();
$ This-> thirdparty_wt_wc_pdf_invoice_init ();
$ This-> thirdparty_bewpi_invoices_init ();
$ This-> thirdparty_yith_pdf_invoice_init ();
$ This-> thirdparty_wc_delivery_notes_init ();
} // << this line
// END THIRD-PARTY PLUGIN SUPPORT

	function thirdparty_get_invoicenumber($default, $orderid) {
		if ($this->invoicenumbers_activated()) {
			$_of = new WC_Order_Factory();
			$order = $_of->get_order($orderid);
			$number = $this->get_or_create_number($orderid, $order, 'invoice');
			return $number;
		} else {
			return $default;
		}
	}