Custom code for displaying customer note in documents-PDF Invoice/Packing slip

functions.php

<?php
add_filter('wf_pklist_alter_additional_fields','wf_pklist_add_customer_note_invoice',10,3);
function wf_pklist_add_customer_note_invoice($extra_fields,$template_type,$order)
{
	if($template_type=='invoice')
	{
		$cust_note=$order->get_customer_note();
		if(!empty($cust_note))
		{
			$extra_fields['cus_note']=$cust_note;	
		}
	}
	return $extra_fields;
}