diffence in page # when exporting from pages to MS Word

There are a lot of reasons as to why this could be, to name a few

different page sizes (i.e. US Legal - A4)
different margins
spacings
breaks
fonts
sizes

In all honesty it is hard to simply guess without seeing the document, but the actual question would be does it matter? And if you are going to have to export it from Pages to Word why not write it in word in the first place to avoid such issues.

Does the document have to be in word format or could you use the pdf option

 

Okay, I think this happens because of the way Pages handles word documents differently from Word. Its the way they put the lettering on the page (subtle differences in letter spacing, line spacing etc). make the difference.

Take any full (one) page document from Word and open it up in Pages and I can guarantee that it will either be 1 page and a bit, or a little shorter than the full page.

You'll just have to rejig the document to make sure it fits the way it was.