Thanks Bertone, that's great! I did as you suggested (the two patches in order) and the odd/even option is back. I'd installed it previously, but as you say, installing the latest firmware patch (UPD 2013.04.29) afterwards meant it reverted to the earlier version of the pdfreader. All working now, and I've got to say, the odd/even margin system is easy to use and works perfectly. There's an 'instruction' video of sorts on youtube
here.
Thanks again for your quick help.