It is not necessary to manually mark each change of the latex file. One can edit directly in the tex file, using latexdiff to mark the changes texts. One drawback is that when changing the titles of the figures and tables, the changes would note be properly marked.

The command line for generating the marked tex is:

latexdiff origin.tex modify.tex > diff.tex

origin.tex is the original tex file. modify.tex is the changed tex file. diff.tex is the tex which could show the changes of the texts.