Why use an editor?

Using an editing and proofreading service has several advantages:

Mistakes spoil the first impression of any piece of work, undermining your credibility.
A trained proofreader knows how to look for mistakes.
Software may draw attention to obvious errors, but the correct spelling of the wrong word might not be highlighted. My favourite real world example: a book ready for publication about nursing the accurately ill. It should have been the acutely ill.
Misused words can cloud your message. This poem is an example of the problems that can arise.
To reach your target audience you need to express the message clearly and concisely, using the right words.
Using your own time, or the time of your employees, for what you do best, and getting a professional for the final review makes the best use of your resources.
A Graphic Designer is concentrating on making the result look good, which is an entirely different task from spotting errors.
In 2005 Royal Mail published a survey that showed 74% of their sample wouldn’t trust a business that used poor spelling and grammar.

“It was incredibly easy to work with Sarah as a proofreader thanks to her swift responses, fast turnaround, and professional approach. She was proactive in suggesting solutions to addressing issues she found in my writing, and I appreciated the gentle and friendly tone of her comments”
Dr Anna Bull, University of York.