Proof-reading for typographical errors, punctuation, grammar and spelling.

General Editing for consistency of style and presentation in both content and formatting.

This makes documents easier to read and includes proofreading.

Structural Editing for ensuring overall consistency of style and readability, and for ensuring that the document will succeed in communicating with its intended audience.

This may include re-writing of sentences or paragraphs, and re-structuring of the document.

This level of editing, which includes proof-reading and general editing, is particularly useful for documents contributed to by several people or by those for whom English is a second language.