watermark

[llocani]

i'm trying to add an image to every pdf page.
With another library i'm getting it with this css:
content: "";
position: absolute;
z-index: 9999;
top: 0;
bottom: 0;
opacity: 0.5;
left: 0;
right: 0;
background: url('data:image/jpg;base64,.......') 0 0/100% 100vh;

But not with pechkin.
So two question, is vh supported by Pechkin? Is there any other way to get an image in every page?
Thanks in advance!