We have a civil war diary from an ancestor. Its very faded and has been wet at some point. What can we to to try and persevere it or read it. I realize it's not some great cultural artifact but it would be interesting to be able to read some of it.
So here are some basics about preservation.
First, try to wash your hands before handling the paper, because the oils on our skin can seriously damage paper over time. Try to keep it in a relatively low temperature area, as well as keep it away from direct sunlight, as sunlight can change the color of the paper. Obviously you can't fully control the humidity wherever you store it, but try to keep it at a relatively average/low humidity if you can. I would suggest storing it in some type of document box to keep it from being damaged.
In terms of trying to read it, if you have a local historical society, try to ask them and see if they can help. Even just reaching out to a museum with a couple questions may help you read it!
Similar questions about preserving old photos/books/documents pop up here regularly. The important points for all of it are
Storage should be cool and dry, preferably in an acid-free box, out of the sunlight.
It's the information in the document that's the most valuable, so scan and digitize. If you have time and interest, read text and transcribe it. Once a document is transcribed, it becomes much more accessible to researchers.
Documents/photos relating to local history can often be the most valuable to the local museum or historical society, and they will often be the best place to have them evaluated, and often have information about having them conserved, able to refer you to conservators.
Conservation is a good thing. It also can be expensive, compared to the actual value of the item. So, for example, a whole family bible with genealogical information written on the flyleaf would typically not be worth conserving, but the flyleaf alone likely would be.