It's important to have a backup copy of your documents, especially the ones that can't be replaced or were hard to find. You can either make paper copies, or my preference, scan your records. If you have the hard drive space (I have a second hard drive in my computer that's for data only) scan your documents to the computer. You can also scan them to CDs that can be store outside your house, for example in your bank safe deposit box. Some of these scanned documents can be linked to entries in your family tree software for easy viewing.
My preference, scan documents to my hard drive. For photos (see separate thread), I scanned them to my hard drive and then burned them to CDs to share with the family and I also loaded them into the free AOL picture albums so I can share them with everyone. This works for documents too. Some scanners will number your scans 001, 002, etc. so remember to view the files after you scan them and rename the files so you can easily locate what you're looking for.