Pre-Capitalist Economic Formations is part of a huge manuscript Marx wrote in researching and preparing what would become A Contribution to the Critique of Political Economy published in 1859.
Marx's collection of personal notebooks, of which this text was a part, would finally be published for public perusal in Russian in Moscow, 1939-41. It was printed in German in 1953 as the Grundrisse der Kritik der Politischen — or the Grundrisse, or Outline, for short.
Pre-Capitalist Economic Formations is pp. 471 - 514 of the Grundrisse and was published separately in Berlin, 1952, as a pamphlet called Formen die der Kapitalistischen Produktion vorhergehen.