Hi
if(file_exists(HIKASHOP_MEDIA.'plugins'.DS.'invoice.php')){
$file = HIKASHOP_MEDIA.'plugins'.DS.'invoice.php';
}else{
$file = dirname(__FILE__).DS.'attachinvoice'.DS.'invoice.php';
}
The plugin checks the file "invoice.php" in the "media/com_hikashop/plugins/" folder and if there is no file, it will use the default "invoice.php" in the sub folder "attachinvoice" (in the plugin folder).
By modifying the file which is used by the plugin, you will change the result of the new generated PDF.
Regards,