|CD's and DVD's don't work that way. You can't put a Word document on a disc, then go back and modify or edit the document.|
Now one of the problems you will encounter is that once you burn a file to a CD or DVD is that it will make it a read only file, here is the fix Copy the document back to your hard drive or flash drive, then right click on it and select properties. Then take the check mark out of the box next to Read Only. Now you will be able to modify the document. Then make several backups to different locations if it's that important to you.