Hmm...it wasn't an ISO standard, but the standard was freely available both as a download from the web-site and as a book. My printed copy (version 1.4) is fro

Hmm...it wasn't an ISO standard, but the standard was freely available both as a download from the web-site and as a book. My printed copy (version 1.4) is from 2001, and that's a later version, I definitely had earlier, much slimmer books. The 1.0 PDF reference on Adobe's web-site has a Copyright of 1993 and says "First Printing, June 1993". https://opensource.adobe.com/dc-acrobat-sdk-docs/pdfstandards/pdfreference1.0.pdf https://opensource.adobe.com/dc-acrobat-sdk-docs/pdfstandard... And of course there were multiple unlicensed implementations. Famously, Apple switched from Display Postscript in Rhapsody and Mac OS X Server to Quartz and PDF in Mac OS X to remove the DPS licensing costs.