latexdiff - find the differences between two latex revisions
ML-for-NLP discussion on latexdiff
Latexdiff is a tool for highlighting the differences between two latex files. Usage is straightforward on Unix bash prompt:
latexdiff -h for additional options
check diff.pdf for the differences.
Daniel suggested the possibility of using latexdiff as the main diff tool for version control system to avoid storing multiple copies of the same file you are working on.