Changing page numbering formats in the middle of a document is one of the trickier things to do in Word. When you are inserting your section breaks, use the "Next Page" option, instead of continuous or even or odd page options. You might also double check that your section breaks are in the right place by viewing formatting using the paragraph symbol on the Home tab.

I have a long tutorial on my blog for changing page number formats. I hope that helps.

Steven