Interesting insight from some of the people who ought to know.

John Warnock had the idea that every document that was ever printed, or ever would be printed, could be represented in a document. This was not an unreasonable idea since Postscript was designed for this purpose and Adobe also had some code from Illustrator that would handle the fonts and graphics and code from Photoshop to display images. So, Warnok started a project (the Carousel project) on his own initiative to pursue his idea that eventually the whole Library of Congress could be represented in an archival electronic format.

PDF really was a breakthrough technology at the time, and it's hard to over-estimate the difficulty we had dealing with file formats for print before it.

Footnote: Back in the mid-90's I was excited enough about the PDF to launch a whole website devoted to gathering together interesting creative uses of the format. PDFheaven (the site no longer exists, and the blogspot site using the same name is unconnected) had origami, art projects, beautifully-designed brochures, calendars, and so on.