Armistice in Korea
Department of State. August 1953. S 1.38:61.
Often the "same" document will be published in multiple sources from multiple agencies within the government and it is up to the user to decide which version is the one that will work for them.
For example, this publication includes the text of the armistice agreement with Korea, plus related materials. Probably most useful for research, but not the official version. The official version of the armistice appears in Treaties and Other International Agreements Series S 9.10: 2782, also from the Department of State. So, if you had to have the "real" thing, then you would go the Treaties... series.
However, you can also find the text of the armistice on the Department of State website at Korean War Armistice Agreement. Same agency, same agreement, certainly an official government website - does this version count as the "real" thing? There's no firm answer; for a class paper, it might be fine; in court, probably not.
Plus, the National Archives and Records Administration hosts an educational site at Armistice Agreement for the Restoration of the South Korean State (1953) that includes the agreement text plus some supporting material, although not the same material as is in Armistice in Korea. Is the Archives material adequate? Again, no firm answer.
Armistice Hall, North Korean Side. Source: Library of Congress.