Can anyone help me with this issue:

I'am using an image that has the same size as A4 paper and it must be placed on top.
So I tried to use the header and activate the image in the header. I set all margins to zero.

When exporting this sheet to pdf or save as PDF I expect my image from left to right and exactly at the top. Unfortunately I encounter margins, like i am printing on paper.

In MS word it works perfectly, so what is the trick to do the same in Excel? I am using Excel 2016

Regards,
Ivo