For GLM manual I have been using multiple text processing programs and versions of LibreOffice and Word. I can't say it has been without issues especially on the regard of the formatting.
I have been using Google Docs for a while, it's quite simple but it basically all I need. That's why I decide to put the GLM manual on Google Docs and I thought it would make easier for GLM users to add some contents or to fixe some issues. Editing is allowed to anyone as far as we have a Google account.