Unless your printer supports full-page bleeds, you'll need to have one or more margins set to around 0.25in (6mm). Do be aware you can use Word's '2 pages per sheet' and '4 pages per sheet' print options to shrink the output to fit two or four flyers, respectively, to a page. And, if you insert a rectangular autoshape into the page header sized to the page dimensions (or slightly smaller), centred on the page and positioned 'behind text', the output with produce a border between the flyers that you can use as a cutting guide.

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Cheers,
Paul Edstein
[Fmr MS MVP - Word]