Let's assume you have completed Stages 1 and 2 of editing a large report. That means you have sorted out the big problems, and have edited the report for purpose, structure and content. You have also edited at the level of headings (headlines), sub-headings and paragraphs.
Now to tackle Stage 3: copyediting for correctness, clarity, style and tone.
EDITING: STAGE 3
Consider sentences, phrases and words—are they OK? If not, fix them now. Use plain language and follow your in-house style guide.
According to what you discover, you will do some or all of these: