If you want to make a good impression, you need to make sure that your documents are polished and professional, with every element right where readers expect it. Think about how you prepare for a job interview. You wear specific kinds of clothes. You carry specific accessories, depending upon your field. You make sure that you look polished, not wrinkly. Everything is exactly right and just as the interviewer expects it. Nothing is missing.
If you need help polishing your work, check out how to Make Your Boring Documents Look Professional in 5 Easy Steps, from The Visual Communication Guy. His post demonstrates easy changes you can make to jazz up your documents.