latexdiff makes a diff of an old latex file and a new latex file and gives a new diff file. The diff file can now be compiled and will show all the additions and deletions in the new file compared to the old one.

latexdiff old.tex new.tex > diff.tex
pdflatex diff.tex

latexdiff might fail if the encodings of the old and the new tex files are different.

To convert a text file with Windows line endings to unix line endings and encoded in ASCII:

iconv -f CP1252 -t ASCII//TRANSLIT windows-CP1252.txt | dos2unix > unix-ascii.txt

Use the TRANSLIT option to overcome issues related to failed encodings of certain characters.

Use git-latexdiff to compare two version of the document in version control. For example, suppose that you are writing a paper. You call the paper paper.tex and just sent a version, after committing it, to your supervisor for corrections. Your supervisor has sent back paper.tex with corrections and comments. You can now just overwrite the old paper.tex with the new one and do:

git-latexdiff --main paper.tex <sha-of-old-commit> --

This will compare the old commit with the one in the working directory (represented by --).