Hi Shelby, thanks for your answer,
there is a test at this url: https://www.lesatheneennes.ch/reservations2017/essai/
where you can buy the first item freely.
You can download the PDF just after the order on « Télécharger votre billet ».
The PDF is displayed correctly on Mac but not on Windows.
I tried to write to the DK PDF plugin creators and they are also searching for
an answer. But it seems that the problem happen when the PDF is generated with
the plugin Event Ticket Plus.