I just posted an answer which has solved this issue:
https://superuser.com/questions/92346/okular-on-ubuntu-9-10-prints-
multiple-pages-per-sheet-n-up-very-small/1062051#1062051
Basically you should select the "Fit to printable area" option...
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This bug is probably not an okular bug, since evince also has the same
behavior
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Bugs, which is subscribed to okular in Ubuntu.
https://bugs.launchpad.net/bugs/504441
Title:
okular prints tiny pages using n-up
This happens to mee too. I keep (the discontinued) Adobe Acrobat
especially for printing multiple pages on single sheet, which Okular
prints too tiny, with too much white space around and in between the
pages.
** Changed in: okular (Ubuntu)
Status: Expired => New
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[Expired for okular (Ubuntu) because there has been no activity for 60
days.]
** Changed in: okular (Ubuntu)
Status: Incomplete = Expired
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