One person in the company buys the latest version and sends you a copy of the document he made with that version. In order to read it, you too have to upgrade. Well, there is not need to go on, as everyone knows this particular song and dance. The point is that with HTML documents you never need have a document go out of date. HTML is an open standard, and all decent browsers, which are usually free, support the code you produce with an HTML editor.
Proprietary formats tend to become outdated.
We can read documents that are two or three versions of a product old. The documents created in proprietary word processing formats have a built in obsolescence, even if you do commit to using the same brand over a long period of time. I recently tried to open some documents that I wrote back in the late eighties when I was using WordPerfect 4.2. My first thought was to open them in my current version of Word, which generally has support for older WordPerfect documents. Fortunately, I have copies of WordPerfect laying around, and I'm sure I will get these documents open eventually.