I would dampen a soft rag and gently rub it but not so much that you peel the paper.
Then I might dab some bleach on it and quickly blot it. When it was a clean as I could get it. I would iron the pages flat.
I did this with a library book that had some tea spilled on it. I went thru the pages and blotted them as dry as possbile. Then I shut the book and put bricks on it to flatten the pages for about 20 minutes. I flipped thru the pages and dabbed with a tissue. When dry, I dabbed them with bleach and then ironed them.
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