DARPA will provide seed funding of $1.3M for research and prototyping centered on reinventing the PDF specification and delivering on the benefits of defining file formats using unambiguous machine-readable assets.
Matthias Valvekens, the ISO project leader who led development of ISO 32004, has written a pair of blog posts to explain what ISO 32004 does and does not achieve in leveraging MAC technology for securing encrypted PDF files against tampering.