Editing can be a final touch or an intervention in the structure, the tone and the argumentation of a text. It spans from a last proofreading to ghostwriting an article on the basis of notes or an interview.
The depth of intervention depends on the quality of the initial text – and also on what your needs are. Not every text has to be a finely crafted structure. But every text has an architcture and it should be solidly built. And not a punishment to read.