Kind of confusing
I use Microsoft office for mac (both 2008 and now 2011), primarily because I need outlook (and previously entourage).
Today someone came to me with a question about printing from numbers at home, I showed them in excel how I would click print, then scale to fit, and it would just come out naturally fit to the page.
He was somewhat confused, so I popped in Numbers, and realized that it was not quite the same process.
To get things to 'scale to fit' on a page, do not use the automated 'scale to fit' found in the print dialogue, I believe that feature is intended for 'scaling down' large documents to fit on a single page.
To scale a page for printing in Numbers, Do the following:
1) On the upper left hand side you will see a "view" box.
2) Click the view button
3) Choose "Show Print View" from the drop-down.
4) At the very bottom of Numbers you will see a Content Scale Slider
5) Scale it to fit the page (some parts will likely bleed onto other pages)
6) Choose File -> Print.
7) Under Pages: Choose Only the pages you scaled to fit (don't select 'All')
8) Hit print, and enjoy your pages being scaled the way you desire!
I hope this helps someone! Seems to be a common problem.