Well, I'm not sure if Equation Editor would work with Pages since it is a Microsoft product and comes with the Office. I might be mistaken but this would seems to be a case of apples and bananas. 

On the other hand if you have LaTeX installed in your system and are familiar with it then you might try to use a small and free utility called [LaTexit](http://pierre.chachatelier.fr/programmation/latexit_en.php). You can check [this explanation](http://www.tuaw.com/2009/08/18/using-latexit-to-display-math-formulas/) to get you started on using equations in Pages.