It seems that the majority of readers believe that Ramsay wrote the Pink Letter. I don't buy it, I think Stannis was the main architect with some input from Mance, but I would like to leave who aside for the purpose of this debate. I'm more interested in testing the Ramsay Theory.
Unfortunately the Ramsay Theory, though widely accepted, does not exist in any unified form, but rather as a separate set of objections to other potential authors. The letter is signed, Ramsay Bolton, Trueborn Lor