OK, I realise this is post is for a niche audience, but after spending 1.5 hours trying to figure this out, I thought I might as well save some others some pain.
I've just upgraded to Microsoft Office for Mac 2011, and, according to Microsoft (see below) it doesn't include the previous functions to create a booklet:
The Microsoft support team were quick in responding (thank you, Jess) – in fact, they responded before I finished this post! Here's a link to their workaround, or you can try my method, below.
For me, there were two challenges: 1. creating the booklet, and then 2. getting the pages to rotate correctly when printed.
Here's what to do:
1. Create your document in Word Mac 2011.
2. Click ‘File', then ‘Print', then click on the ‘PDF' button, and select ‘Create Booklet':
3. The booklet will automatically open in Preview. You now need to ensure the following two finishing options are selected:
Don't choose ‘Booklet Options', ‘Long Edge (Left)', ‘Long Edge (Right)', ‘Rotate Print Data 180 Degrees' or any other combinations or options! Just choose ‘2-Sided Printing' and ‘Short Edge (Top)'. Also, make sure the page orientation is kept as portrait (and not landscape).
4. Press ‘Print'.
Hopefully I can save you the time I lost fiddling around trying to figure it out!
If you receive an error referencing ‘universal', visit this link to download a more recent version of the plug-in.
Unfortunately I'm unable to provide on-going support for queries relating to this function. For any questions, please contact Microsoft Mac Support.