The Buzz Aldrin and Edison ones are indeed official Apple advertising posters:
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I believe you are correct for the smaller 11"x17" size which were only available in the Educator Set of 30 (3 copies of each of the 10 posters) sent out to schools during the original campaign.
The larger 24"x36" (portrait or landscape) original 10 and the following years when they featured other iconoclasts was the only size for general purchase from Apple. Any poster not these two sizes is 100% fake unless it's much larger like the bus shelter outdoor ones in the pics above. Genuine 24"x36" ones go for upwards of USD $300-400 each now. And I don't have a single one.