The Ldiff (LaTeX diff) script takes two LaTeX (or LyX) files as input and generate a PostScript file that contains the changes between the two files: Text that appears in both files is shown in black, text that appears only in the first file is shown in red and is crossed out, and text that appears only in the second file is shown in blue. Note that in some cases, Ldiff will not give correct results.

The author is Dekel Tsur.