Make sure they are stable enough not to tip over to the water. Place the lid on the container and leave it alone for several hours. Put it in a spare room and close the door. After several hours, check the paper. Flex it to check how well it unrolls, unfolds or just feels right.
Some papers hydrate very quickly.
I have already left a super thick post-Victorian wedding certificate in as long as 24 hours, but many papers hydrate in six. Purchase white blotter paper in an art supply store. Lay one sheet of blotter paper down on a table, and spread the documents flat as possible on the blotter paper. Check to make sure folded edges are unfolded, and torn edges close together. A set of stamp collector tweezers is perfect for this job and other steps to follow.