Someone asked me about this today, so I thought I’d pass it on:

When you are writing numbers, generally one thru ten are spelled out. The rest aren’t. So we spell “seven”, but not 17.

I break this rule often, though (it’s not really a rule, but more of a handshake agreement.) Why do I break it? Because “we handle any size job, from 3 pages to 300″ catches the eye better than “we handle any size job, from three pages to 300″ (although the second one actually looks more professional when reading - so it’s really about what you are after - scan-ability, or a professional read.)

Anyway, just thought I’d share that.