I have recently moved from openSuse 11.3 with okular 0.10.4 bundled to openSuse Leap 42 with okular 1.1.2 bundled.
In my old installation I used to click on File->Print, then Options, then Pages and select Pages per sheet = 2 to print two pages on one sheet. In the new installation the "Pages" options seems missing and is not mentioned in the help.

Was it removed (bad idea) or is it hidden somewhere ?

Most of the printing features come from Qt, so please try to upgrade to a new version of Okular and Qt. Maybe there are some additional repositories for openSUSE, or a new version of openSUSE, but that's probably the only way.

Sorry I said I just upgraded to the latest bundled version compatible with my OS, and that a feature which was present in the older version seems to have disappeared

I read that, but:
- the last version of openSUSE Leap is openSUSE Leap 15
- there are additional repositories with newer versions: https://en.opensuse.org/SDB:KDE_repositories

There is no much that we can do on the KDE side.

Leap 42.3 is the latest supported by my institution.
Just for curiosity (since I thought this to be primarily an okular forum) can any okular developer confirm whether the Pages per sheet option was actually removed from okular 0.10.4 to 1.1.2 (which seems an odd thing to do), or whether that was a decision only for the version of okular bundled with opensuse ?

I did not made much use of okular, only to print occasional pdf documents flagged "secured", which actually were printing-enabled but the combination acroread-CUPS occasionally failed to print. Apparently evince has the pages per sheet option, and qpdf can be used to remove the secure flag, so I have found solutions to my issue.

The printing option are provided by Qt, and the support for them was not always good. Many fixes to the printing support of Qt were applied in recent versions of Qt.