Laserfiche backups are there to help you recover from a disaster such as an earthquake causing the building with your datacenter to fall over. If that's what you want to do, I'd recommend taking a look at the Repository Backup & Recovery section in the documentation. Also, Zachary Buck taught an excellent class at EMPOWER. You can still get some good information from the slide deck.
Probably a reason why you can't find much in the way of guides is because the process is going to be different for each implementation.
Basically a backup looks like this:
- Backup the file system data
- Backup the SQL data
You'll need some way to synchronize this with the file system data, otherwise you'll end up with images that have no documents or vice versa.
When you've got a reasonably synchronized repository, you should be able to restore them using whatever tools you have available, and hook the repository back up.
The scenario you present about restoring individual documents could prove to be very difficult, or even impossible, depending on your environment. One question I have, and maybe somebody from Laserfiche can chime in, is (given Rio) is it possible to attach a restored repository alongside the production one on the same server? It should be possible if you have a second server. The reason I ask that is because you might be able to get both the image and SQL data back, but you can't make actual documents out of them unless you hook them up to the Laserfiche server in order to hook documents back up to the pages and metadata. You could do it manually, but it wouldn't be fun or fast.
Making sure that you don't have to do that sort of restore is, of course, a wetware issue. ;)