ISO 32000-1 is the first ISO specification for PDF. The document is an ISO formalization of Adobe's own PDF Reference 1.7, and is technically identical to the Adobe document.
On submission of PDF 1.7 to ISO for standardization in 2007, Adobe issued a summary of changes. (PDF). ISO TC 171 SC 2 WG 8, the Working Group responsible for development and management of the PDF format, stated in 2008:
The US National Body committee that proposed and is supporting the work of TC171/SC2 with respect to the work item ISO 32000, wishes to communicate some background information with respect to this work and urge you to support this work in your own national body deliberations.
In preparing ISO/DIS 32000, Document management - Portable document format (PDF 1.7), PDF Reference 1.7 (including associated errata) was edited to create a document that is both easier to read and understand, and more in line with the style requirements of the international standards community. The key goals during that process were to ensure that the resultant document was technically consistent with the PDF Reference 1.7 published by Adobe in November 2006 and to also incorporate the interpretations of that specification provided by PDF application developers. We supported this action.
The members of the US technical committee who have reviewed the ISO draft and PDF Reference 1.7 agree that these documents are technically consistent. (emphasis provided)
As with previous versions, Adobe's PDF Reference, PDF 1.7 was (and remains) freely downloadable from Adobe.com (as is the document's errata). By special arrangement with ISO, ISO 32000-1 is also available at no charge from adobe.com.
Adobe's summary of changes between Adobe 1.7 and ISO 32000-1.