It is not possible to adjust margins to zero in the printing dialogue. This seems to be different to previous versions I used. I use openSUSE leap 42.3 with okular-17.04.2-3.1 from Fr 22 Dez 2017 15:12:41 CET
In the meantime I found a workaround: In the my default installation (german) the paper size is A4. Here, the adjustment to zero margins is impossible. However, after switching to letter size, an adjustment to zero was possible which, fortunately, is kept when switching back to A4.
I know about this bug, but Okular simply uses the standard QPrintDialog class for its print dialog. Therefore, it is much more likely that the bug is in (the vicinity of) QPrintDialog.
Indeed. See upstream bug report: https://bugreports.qt.io/browse/QTBUG-3546 *** This bug has been marked as a duplicate of bug 374406 ***