There are three levels of editing, with fluid boundaries. They are:

1. Basic proofreading almost always includes light copyediting. It includes catching typos, incorrect word usage, grammatical errors, mistakes in punctuation, and checking consistency. At this level, I’ll go through your pages at an average of 8 pages per hour (assuming 250 words a page). The charge is $25 per hour (about $4 per page)
2. It may be that your project requires line editing, which includes all of the above plus suggestions on word choice, tone, flow, tense, point-of-view, sentence structure, and clarity. I include fact-checking when I line edit. Line editing, also known as a moderate copyedit job, takes longer. I’ll go through your pages at an average of 5 pages per hour (again, 250 words per page). Charge is the same, $25 per hour, but ends up more per page—about $5 per page.
3. Content editing, also called developmental or substantive editing, includes all of the above plus organization of content; references to illustrations and charts within the text; restructuring for transitions; analysis of point-of-view within each scene (fiction); cross-checking references, equations, and tables; and more fact checking. This kind of editing typically takes about an hour for every 3 pages. I charge $30 per page for this in-depth editing; with an average final cost as much as $10 per page.

I promise you that you’ll see a huge difference in your final product. Everyone needs an editor.