Hi,
The PDF that you provided come from the invoice PDF plugin. So it's not a view of HikaShop that you need to edit but the file plugins/hikashop/attachinvoice/attachinvoice/invoice.php of the plugin.
That's why you didn't see any difference. I'm sorry but if you don't provide all the necessary information for us to understand your situation, it's hard to tell you precisely what to do...
So you need to replace the code:
<?php if(!isset($order->order_invoice_number)) $order->order_invoice_number = $order->order_number; ?>
<div class="invoicetitle"><?php echo JText::_('INVOICE').' '.$order->order_invoice_number; ?></div>
by:
<div class="invoicetitle"><?php
if(!empty($this->element->order_invoice_number)) {
echo JText::_('INVOICE').': '.$this->element->order_invoice_number;
}
echo JText::_('ORDER_NUMBER').': '.@$this->element->order_number;
?></div>
in that file and you will see the modification.
Regarding the file name, you can change the line:
$invoiceFile = JText::_('INVOICE').'-'.$orderid.'_'.time().'.pdf';
to:
$invoiceFile = JText::_('INVOICE').'-'.$data->data->order_invoice_id.'_'.time().'.pdf';
in the file plugins/hikashop/attachinvoice/attachinvoice.php