Recent
Tracking changes in LaTeX with "changes" package
The changes package, distributed with TeX Live, allows the user to manually markup changes of text, such as additions, deletions, or replacements. Changed text is shown in a different colour; deleted text is crossed out. The package allows definition of additional authors and their associated colour. It also allows you to define a markup for authors or annotations. (Here's another customised example using avatars for the author annotations.)
LianTze Lim
Track Changes in LaTeX with trackchanges
Note: TrackChanges is not part of TeX Live, and hasn't been updated in a while. Instead, changes.sty, a package for the same purpose, is available in TeX Live and more recent. You can find the example template here.
TrackChanges is a package for collaboratively editing LaTeX documents which allows multiple editors to make changes & add annotations to a document.
Here we present a short example of it's use, which you can use as a template to get started.
writeLaTeX
Tracking changes in LaTeX with "changes" package (with author avatars)
The changes package, distributed with TeX Live, allows the user to manually markup changes of text, such as additions, deletions, or replacements. This example customizes the package to show author annotations with avatars. (Here's a more conventional example without the avatars. )
LianTze Lim