I was just wondering really. But if anyone has or knows of software that assists, if not creates, with the creation of a GDD, please share.

Apart from MS Word?

You may want to employ a combination of Word, Excel (or Google Docs/Sheets) + some mind map software for brainstorming + wireframe software (Balsamiq, Pencil, etc) for sketching screens + diagram software (Visio, Dia, etc) for game flow + possibly some UML software for architecture design.

All of these can be part of a game design doc but I have not seen any software that combines all of this in one package (probably would not make much sense either).

The closest thing I've seen for design software is articy:draft (http://store.steampowered.com/app/230780), but it doesn't really help create a GDD per-se (and it's $99USD.)

Microsoft Word.

No, really.

If you're doing more than a few pages you're doing it wrong. See for example the original design document for the first gta game:

http://ocw.metu.edu.tr/pluginfile.php/7939/mod_folder/content/0/RaceNChase.pdf

I often see people spending months producing hundreds of pages on their game before stating writing code. This is just wasting time, designs need to be simple and flexible.

Two cents worth firmly inserted into this conversation...

Well the OP of this thread seems to have made some GDD creation software. I thought it was interesting. So, again, I wondered if there was anything else like it. But it seems most people just use a collection of tools.

I use a (physical) whiteboard as well, I set aside a wall of my home office for it a few years back and found it invaluable both for my day job and for game dev.

With all due respect to ModernToMe, I think he is solving a problem that doesn't really exist. If your GDD fails to be of use to you it will definitely not be because you forgot to include the company name or team size. And like braindigitalis said, you need to keep it flexible because the design can and will change.

We combine google docs with mindmap software & spreadsheets... that's about it :)