Hi,
1. The PDF files as attached to the emails based on the order status of the order and based on the "Statuses for email attachment" setting of the PDF invoice plugin. So make sure that in this setting you have the status of the order for which you're doing your test. Also note that the PDF will only be attached to the order status email notification (which is sent when the status of the order is changed) and the order creation email notification (which is sent when the order is created). It's not attached to the order admin notification (that you receive as an admin when the order is created), the payment notification (which is sent to you as an admin when the payment notification is received) or to the order notification (which your customer receives when you click on the "email" button in the backend order details page.
2. The layout of the PDF invoice has to be different from the invoice you get without the plugin.
That's because the PDF library we're using in the plugin requires the code to be in a specific way and it's not possible to directly use the HTML of the normal invoice and make it a PDF. Only a real HTML rendered like there is in your browser could do that but it's way to complex to develop that.
So that's why you have a different look. You would have to modify the file plugins/hikashop/attachinvoice/attachinvoice/invoice.php if you want to customize the look of the PDF invoice. You don't necessarily need to be a developer to do these changes. It's mainly about adding CSS code to the invoice.php. A web designer should be able to do that.
If you don't know CSS however, I'm afraid you'll have to hire someone to help you with that.