Outer margin on left-hand side booklet page is much bigger than it should be

Hey guys

I'm trying to print a small booklet I created in LaTeX using the book class. Using the [twosided] option it adjusts margins so that the outer margins are each the same as the inner margins put together, and when I typeset the pdf, this is the case and it shows up well in Reader.

However, when I print the booklet, the outer (left-hand side) margin in the left-hand side pages is much bigger than it should be, pushing the text all the way into the middle and up against the crease when I fold the pages.

I've tried adjusting the options on the LaTeX file and it all looks like it should in Reader, but something happens when I hit print -- the margins keep coming out weird on the left page yet (apparently) correct on the right-hand page.

Any suggestions?

Thanks!