Why would I need to use version control with my LaTeX documents? I know people who do it, and I've seen questions about it on here and on SO, but I haven't understood what value there is to doing it...
[Maybe this should be CW?]
As a single user the main advantages are
I'm also someone who uses version control as a single user. All of Caramdir's reasons are ones that I agree with, and I'll add the following:
Incidentally, I switched to using a version control system around about the time I started taking online notes of everything that I did. So I wrote up some notes on the process here. I also found an article (also available as a wikibook) on the subject that was very helpful to me in deciding to switch to a version control system and on what to look for in one.
Using revision control makes you unafraid to make radical changes to your document. As one of my friends, Peter Boothe, put it,
you can now freely throw away bits and pieces, secure in the knowledge that if you actually want them back, they are there in the revision control system. Interestingly, almost nobody actually uses this feature. Revision control systems are not there to save your old work. They are there to give you permission to throw that old work away.
For me, one of the main reasons for using a VCS is to avoid cluttering my working directory with lots of mainly useless files with cryptic filenames like:
With such a system, it is hard to keep track of which changes occurred in which version. It gets worse if you have multiple authors collaborating on a document with different file naming conventions. It gets even worse if you are using a similar system for your bibtex and image files, as you have to keep remembering to update the references to the files in the main document. It gets even more worse if you are collaborating via sending email attachments and don't know for sure that you have saved every single version that was emailed into your working directory.
With a VCS you just have one copy of each file, so you have a much cleaner and easier to navigate working directory. The VCS should make it easy for you to find out where changes were made, so that you can easily find things when you want to restore something that you previously edited out. Since the VCS stores everything, you know that every version of the file is available in one place. It should also declutter your email inbox a little bit as you won't need the attachments and emails that just announce updates to the document are no longer needed.
If you haven't used a version control tool before, I seriously recommend you start using one. Otherwise you will version control manually i.e. paper-v5, paper-v6 etc which may be sufficient for one-off, short-term projects.
You can see version control as recording a (discrete) history of your project allowing you to associate notes with the changes you make and to inspect at later stage why they were made. This might sound cumbersome but most good editors let you seamlessly integrate it into your workflow. In fact you will soon find version control tool indispensable.
For why this is needed, look at the other (very good) answers. I would like to add that I use DropBox for my LyX documents. It does pretty much what you would get with a VCS (without branches/merges etc. - but as a single use for a document, you probably won't need it), but it does that automatically. It syncs your files between computers and it makes your documents available to you online.
I agree with the others, but the most "non technical" reason is to think about it as "unlimited undo" between the versions that was saved in the VCS.
You can always get a old version back regardless what you do.
This is the meaning of the "automatic backup" that is a little bit tricky to understand.
SubVersion is a simple to understand system, that works well for small teams.
Git on the other hand is is more technical advanced and scales better, but for small teams this is a academical question.
But the point is that any VCS is better than not using this type of systems at all.