This is amazing that they are even readable. I havejust come into possession of a diary and some albums belonging to my great grandparents — the oldesr piece dating from 1862. Most of the writing is so faded that I can barely make it out. It was written on acid free paper in those days, but most of it is written in pencil which is really dim by now. I have a big job ahead of me to transcribe it.
Good luck. You may try running it on a copy machine with the toner turned on high.
I suggest you try scanning them and then using Photoshop or any other decent imaging program to bring up the text. If that doesn’t work you might try to find a professional conservator or perhaps a local library or university. If my memory serves, the pros use thermal imaging to get good recovery of the faded text. Good luck.