The ISO released the 2.0 version of the specification that replaces the 1.7 standard.
"Although it is an open standard, one major difference compared with prior versions of PDF is that ISO now holds the copyright to the PDF specification and thus PDF 2.0 is not freely downloadable." [0]
It looks like DMCA requests are being issued to anyone that hosted the old specification, even open source projects [1].
[0] https://www.pdfa.org/resource/iso-32000-pdf/ [1] https://github.com/Hopding/pdf-lib#git-history-rewrite