Many people mistake editing for proofreading. While editing includes proofreading, the two are not the same thing.
Proofreading tends to be error focused, and is usually a local errors approach. Editing is more holistic, requiring both a local and global approach to any given text. Editing requires that the editor not only correct “errors” but help the author maintain good organization and clear presentation, all while maintaining the author’s voice in the text. A good editor “disappears” from the page, much like a good fiction author is never noticeable when one is deep into her or his stories. A good editor asks questions and marks changes so that the author has all final say. A good editor knows she is not in charge of the text, she is merely there to help bring it to its best form.
Much like indexing, good editing requires several read-throughs. Always, the first read is to gather a sense of the text, as well as a sense of the authorial voice contained in the text. While an editor may mark points to return to during the first read, she will not make changes at this stage, except proofing for obvious typos. Changing entire words (as opposed to correcting spelling) at this stage can be dangerous, as one is still not fully aware of the full thrust and internal workings of the text.
I go through at least three reads of any text I’m editing. I enjoy editing, and in fact, find that I often feel compelled to edit (you should see my books! I correct typos in published things, too!). This is because my dyslexia makes it impossible for me to read as most people do. Most readers grasp about 2/3 of the length of a given line in a standard paperback book. This means that unless you are practiced at editing or, like me, you are dyslexic, you rarely notice words that are “out of sorts.” In fact, studies have shown, and internet memes have made common use of this, that even if every word in a sentence were scrambled, so long as the first and last letter of each word was in its correct place, the vast majority of people would read the sentence with only a slight level of discomfort. Being a dyslexic with four advanced degrees has helped me become a careful reader. But being a dyslexic whose Bachelor’s is in Journalism is what made me a good editor. I’m proud to be both.
There is one catch, however. No person is capable of editing her or his own work. You may also be a great editor, but—and the studies that showed you could read scrambled words also show this—you can never see your own work in as clear a light as you can the work of someone else. You are simply likely to read what you expected to, having written it in the first place.