You Are the Expert
When a professional gives their work to an editor, they are not handing over responsibility for what it says.
A consultant may be writing about a field they have worked in for twenty years. A lawyer may be explaining a point of law. An architect may be describing a project. The editor may know very little about any of those subjects.
That is not necessarily a problem. The professional brings the expertise. The editor brings a different pair of eyes.
An Editor Doesn't Need to Know More Than You
An editor does not need to become an expert in your profession to recognise when something on the page isn't working.
A sentence may contradict something you said earlier. A specialist term may appear without explanation. An argument may jump from one point to another without showing the connection. A conclusion may make perfect sense to you because you already know the information behind it.
The editor can identify those problems without pretending to know the answers.
If something is unclear, they ask.
Your Name Is on It
This matters particularly when you are writing under your own name.
An article, report, professional opinion, presentation or consultancy document may be read because of your qualifications and experience. The reader assumes that the statements and conclusions are yours.
Editing should not change that.
An editor can make a complicated sentence easier to follow. They can point out a contradiction or question something that appears to be missing. They should not add an explanation they think is probably correct or strengthen a conclusion because it sounds more convincing.
You need to be able to stand behind the finished document.
Specialist Language May Be Necessary
Not every difficult word needs replacing.
Professional terminology exists for a reason. Sometimes a specialist term is considerably more accurate than its everyday equivalent, and replacing it with something simpler can change the meaning.
Who will read the document matters too. A report written for other specialists can assume knowledge that an article written for the general public cannot.
An editor can tell you when terminology may cause a problem for the intended reader. You decide whether that terminology is necessary.
A Query Is Better Than a Guess
An editor will sometimes come across something that looks wrong but cannot safely be corrected.
Perhaps two statements appear to contradict each other. A technical term looks unusual. A name or designation differs from one used earlier. Something appears to be missing from an explanation.
The temptation to make the sentence work should come second to making sure it remains true.
A query gives the question back to the person qualified to answer it.
Different Expertise, Same Document
Working with an editor is not about handing your professional judgement to somebody else.
You know whether the argument is sound, the conclusion is justified and the specialist information is correct. The editor looks at whether the English communicates those things properly and whether the document works for the person expected to read it.
Neither has to do the other's job.
You are the expert. The finished document should still be yours.