But don't you need Adobe Acrobat to sign it? I won't fault them for using their own tool.

If we were talking about almost anything else from MS I'd probably agree with you. But this is the specification to a computer programming language, a language that MS has tried over and over to assuage the fears of open-source developers about. "Oh, it's standardized by ISO and ECMA!". "Look, Mono is proof it can be implemented cross-platform!", etc. And then they do stuff like this.

On the other hand look at the excellent work done by Microsoft Research (and then look at what format that final work is usually published in).

As a regular reader of Microsoft Research papers, I can assure there are quite a few of them published in Word and PowerPoint formats.

Quite a few of them are also LaTeX. Generally it's probably the same distribution of formats you see in academia as well. And often the publishing journal dictates what to use.