Formatting of PDF margins only works for top, not bottom

I want to increase the margins for the PDF of a quotation. I have created a new print style (not print format!), with the following margins:
.print-format * {
color: #000 !important;
margin-top:20mm;
margin-right:20mm;
margin-bottom:20mm;
padding-bottom:20mm;
}
However, while adding the margin-top there has the desired effect, adding the margin-bottom and/or padding-bottom has no effect. How to solve this problem?

Best, Till