White space provides visual breathing room for the eye. It breaks up text and graphics. Add white space to make a page less cramped, confusing, or overwhelming.
Is there such a thing as too much white space? Yes, there is. However, its rarely the case in the work done by non-designers and those new to desktop publishing. Usually we try to cram too much onto the page, afraid that well leave out something important. But without adequate white space, the important information gets lost. If all the text and images you want in a document are truly important and there is nothing you can cut out, use a bigger piece of paper.
White space can also be used to set a mood, convey a specific image. If you want a design to say "wealth, upscale, prestgious, or elegant" then use lots of white space. If you want a more down-to-earth, ordinary folks appeal, bring it down a notch or two. If you want to look cheap, mass-produced, or amateurish then fill the page to overflowing.
There are instances when trimming white space to the bare bones can and does work. However, in most cases, more of nothing is better.