I can offer you various editing approaches:
- Good old Microsoft Word with Tracked Changes — The majority of my clients prefer this [example]
- Annotated Adobe pdf — Great for a final proofread of something you’ve already formatted: a presentation, flyer etc.
- Marked-up Adobe pdf — This is one for the hard-core professionals: BSI proofreading markup (to BS 5261C: 2005)
- LaTeX — For Maths / Physics / Engineering / Computer Science papers*
*Please note that I am not aware of a way of ‘tracking changes’ with LaTeX. You get back an edited LaTex source file and generated pdf, either of which you can compare with the original with file comparison tools.