Another suggestion would be to use some sort of distributed source control system to keep track of the changes that you each make.
Dropbox has built in source control, so you can roll back to previous changes, and it is fairly simple to use. Their Terms of Service kind of trouble me, but I may have donned my tinfoil hat in recent years.
- Easy to use
- Easy to get started
- Track changes
- Syncs to multiple machines, making backups easier
- Your work is stored on someone else's servers
- May not be able to see fine-grained changes easily
If you're decently technical, something like git might be a better option, as you can easily see differences between check-ins, and keep track of who is changing what. As a programmer, I use git every day, and that sort of mindset has become second nature to me. This is beneficial when you're working with 10 other programmers/designers, and you need to keep track of who is doing what.
This would also give you the benefit of keeping all of the content on your own systems, making sure that it's not inadvertently copyrighted by some other entity.
The downside might be that Git was designed to work with non-binary files (such as flat text files), rather than proprietary Word files (or other proprietary file formats), so the change tracking might not be best used with Word files.
- Track changes at a fine-grained level
- Your content is always in your possession
- Allows you to keep multiple branches of the same work
- Keep multiple versions in local source control before committing to the main repository
- Don't have to keep multiple, differently-named files to track versions
- Tons of resources to get you started, and keep things going
- Many GUI application options to choose from, regardless of the operating systems used by the contributors
- Works best with non-binary file formats
- Requires more technical knowledge to learn and get setup
See what other writers here on the site think about using source/version control with their writing in this question.