Write down the qualities you think your company has and what message you want to convey. Remember this may be the first and only chance you have to catch a potential customer's attention. If you need help with the copy, you can hire a free-lancer before you find a graphic designer. But if you need help with the copy, concept, production, printing and dissemination, you may want to look into hiring a full-service graphic design firm. There are a lot of firms in between, though.
Some firms can help with the writing and producing.
Others can help with production and promotion. There are advantages to retaining a full-service graphic design firm. Keeping tabs on what is going on at only one place is definitely a benefit. Having a creative team work on a project may be helpful with consistency. It also may cut down on how long it takes to do the project.