Synctoy is designed to work both ways (all ways), thus it's not a classic backup software. However each synchronized folder always contains a copy of another one, so you get file backup with no effort.
Forget regular backup/restore routine. Just synchronize your document folders on primary computer with a backup device, which also can be used for instant read/write access to your data.
As a secondary device you can use a local drive or another computer in network. That will guarantee safety of the files in case of hard drive mechanical failure.
Another option is to backup to a miniature removable device (USB key, Flash drive, etc). In that case your documents will be always with you, ready to view or modify. And losing USB drive won't be a disaster: you got file copies on the primary computer.