Think of a really good print advertisement you've seen lately. What did you like about it? Chances are that while the content of that ad was important, the design played a big role in drawing you in.
It's important to think of your resume like an advertisement to job recruiters. Writing a standout resume goes beyond the content you put in there -- the format plays an important role, too.
To recruiters, it speaks volumes about how you collect your thoughts and organize your ideas. So you'll want to make sure it's easy to read, easy to understand, and easy to digest. That means choosing the right sizing for your headers, picking the right fonts, bolding and italicizing effectively, and so on.