Yea, paper is mildy acidic and starts to yellow and break down immediately after being made. Faking the age of paper is about the hardest thing for a forger. It's like faking a vintage wine. You can get the chemical composition or physical texture right but getting them both right is too difficult. Which is why forgers will often just use stock from the period and carefully remove the inks and overlay new ink. But with something as young as 30 years they could bluff thier way easily. Oss are they're not that astute.
A decent forger would have bought any old typewriuter and done the memo up.
I was looking at some of my old orders and papers from 1991 when I first joined the military. I have kept my important documents in a acetylene document keeper, such as orders and enlistment contracts. They look worse than these documents from 30 years ago, they do not contain superscripting for my unit and there type is more bold. Not to mention even keeping them in a acetylene sleave they still have some yellowing from age.
I find it very hard to believe that a 30 year old document does not contain even a hint of yellowing, if they were photocopies of an original they would show some dark spots from the copying process due to the discoloration.