PDF invoice plugin modification problems

-- url of the page with the problem -- : www.scopeslipstop.com/nl/winkel-2
-- HikaShop version -- : 4.0.2
-- Joomla version -- : 3.9.2
-- PHP version -- : 7.2
-- Browser(s) name and version -- : Chrome

Hi All,

I'm having a lot of struggles to change the layout of the invoice pdf plugin. I've read a lot of history on the forum, but none seems to help.

As soon as I change something in the invoice.php (even when it's just a color), it generates directly 2 pages and the first page is ony a questionmark and the second page is the correct version. I have noooo clue why the plugin is doing that.

Second is that I am able to add a logo, but in the best case scenario I would like to add a full image on the background of the company which I'm working for.

Don't you have somewhere a document where is written how to change things? As these are common questions I assume?

But it starts with the questionmark which is popping up all the time as soon as I make a change in the invoice.php

Thanks

Martijn