Coffeestains: Package to add coffee stains to LaTeX documents
https://ctan.org/pkg/coffeestainsExample pdf: https://mirror.csclub.uwaterloo.ca/CTAN/graphics/pgf/contrib/coffeestains/coffeestains-en.pdf
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Example pdf: https://mirror.csclub.uwaterloo.ca/CTAN/graphics/pgf/contrib/coffeestains/coffeestains-en.pdf