If you just Google for editorial services, you'll get a lot of hits. Who are these people? Do they have a clue? Will they steal your manuscript?
Even if they list testimonials on their site, you have no idea if those are real. You need the word of someone you trust.
When I went looking for recommendations I could trust, I went to Absolute Write. I've been a member there for a while now, though I don't drop by as often as I should. It's an independent forum with a large membership that ranges from complete beginners to professionals with many years of experience in the industry.
If you're looking for a crit partner, writing advice, experts in nearly any field, or you just want to talk about your favorite genre, it's a great place.
One of their best services is the Bewares, Recommendations and Background Check forum wherein you can learn about just about any agent, publisher, or freelancer out there. I crawled through that forum vetting each of the companies that came up in Google, as self-imposed homework for publishing myself.
And I'm going to let you steal my homework. These four companies are my short list for editing Disciple, Part I: For Want of a Piglet.
The Editorial Department
Offers manuscript critique, line editing, and publishing services for fiction and non-fiction. I was most interested in the proofing and line editing, at 2 to 6 cents a word, and the manuscript evaluation at 0.8 cents a word. They'll annotate the manuscript for 1.2 cents a word.
Editing For Authors
Offers comprehensive editing at 1.7 cents a word and proofreading at 0.9 cents a word. Publishing services too.
Based in the UK. They also work with writing for children. Their prices convert to a bit lower than the above two, actually, though some of their rates are hourly. And you have to send them a query.
The Book Doctors
This site was well spoken of on Absolute Write, but their list of services is more vague. They offer consultations as time blocks: 15 minutes for $90, 30 for $150, an hour for $250.
Addendum to the short list.