WHY? >> WHICH DO YOU NEED?
WHICH DO YOU NEED? A COPY EDITOR? OR PROOFREADER? OR BOTH?
Basic publishing steps
A work in words that is intended for publishing goes through certain stages.
The author writes the manuscript, with or without the assistance of a developmental editor, and when it's ready it goes to a copy editor.
The copy editor reads through the manuscript word by word, line by line, paragraph by paragraph, and page by page, and corrects and changes it according to the author's and developmental editor's guidelines.
When the author and publisher are happy with the edited copy, it goes to the production editor who organises the design, illustration and printing of the work, including finding proofreaders to check the copy when it is deemed ready for printing.
The proofreader double checks everything all the other people have done to the manuscript, ensuring that it will look perfect.
Then the work is ready to publish.
Which service do you need?
Have you just written your manuscript and not formatted it in any way?
Then you probably need a copy editor.
Has your manuscript been edited and are you happy with it?
Then you probably need a proofreader to make sure that it looks perfect before you publish it.
But most people want a combined service, especially if the work has already been published on the internet.