If the correspondence does not need to be editable, PDF is the best option, with even less problems than Word or OpenOffice formats. And LaTeX has built-in supp

If the correspondence does not need to be editable, PDF is the best option, with even less problems than Word or OpenOffice formats. And LaTeX has built-in support for it. I agree with revision history, Word probably manages it pretty good. But git repos aren't a bad option if you are used to them. I personally use Dropbox, so I have a simple revision history without problems. Anyways, I didn't say LaTeX was the perfect solution, that's why I said that he maybe had some impediment to use it instead of Office.