It doesn't matter whether you're a small business with a few employees or a massive business with tens of thousands, it's always worth taking a second look for typos. Sooner or later they'll get you, but there are things you can do to keep them to a minimum.
Print it out
While you should do this sparingly to avoid killing trees in droves, there's something about reading words on a printed page that makes typos jump out more than they do on-screen. So, if it's a particularly important piece, like an annual report, it may be worth printing out.
Put another set of eyes on it
The best thing you can do to avoid typos is to make sure that more than one person gives your piece a good read. Even the best copywriter or editor can miss something when they've been staring at the same piece for too long. In fact, when you're too familiar with the material, it can create a sort of familiarity blindness, where you're reading what you think your piece should say instead of what it really says. A fresh set of eyes can disarm this problem.
Put it down and come back
If you have the time, this approach can be almost as good as a second set of eyes. Step away from a piece for a while before editing it. It can give you the chance to look at it with fresh eyes, without all the baggage and context of writing it. Once you shed that baggage, you'll be exponentially more likely to find any typos you may have missed before.
Read it backwards
You won't catch many grammar errors this way, but it does wonders for finding spelling typos and words that simply don't belong.
Don't over-rely on spellcheckers
Spellcheckers are notoriously unreliable. They often don't recognize commonly accepted words, they can't update fast enough to keep up an ever-changing modern vocabulary and all too often they substitute the wrong word when trying to correct for grammar. Remember, a spellchecker is a tool, and an imperfect one at that. Make sure you're using the tool and not the other way around.