Lignin, the stuff that prevents all trees from adopting the weeping habits, is a polymer made up of units that are closely related to vanillin. When made into paper and stored for years, it breaks down and smells good. Which is how divine providence has arranged for secondhand bookstores to smell like good quality vanilla absolute, subliminally stoking a hunger for knowledge in all of us.
This should apply to most paper ephemera too, right? (Provided the old paper isn’t stored in wet or humid places where mildew will overpower any other scent.)