Bryan Lamkin, a long time Adobe manager wrote an article about the 25th anniversary of Acrobat on the Adobe Blog.
He talks about the Camelot white paper written by John Warnock, founder of Adobe Systems, which is considered the starting point of PDF and Acrobat.
Acrobat 1.0 was introduced officially on June 15th, 1993 in the Equitable Center in New York.
In the last 25 year documents have evolved from printed paper pages with text, graphics and images to digital documents including videos, interactive objects and links. PDF was adopted contiously to the changing requirements.