Purple Numbers for PDF documents?

My contribution to Silona Bonewald week was an interview about her new project citability.org. Silona proposes two new features for government websites. First, change tracking. Second, permalinks for documents, sections, and paragraphs.

Nobody will dispute the need for, or utility of, these features. The question is how to implement them across a sprawling landscape of content management systems and publishing procedures that still, in many cases, regard print as canonical and the web as an afterthought.

In a follow-on discussion with Silona, on the citability wiki, I recalled a little-known and rarely-used feature of PDF documents. You can form URLs that point to specific pages. And with the right preparation, you can even form URLs that point to named destinations within pages.

Those of us fluent in web-friendly document formats like HTML and XML will tend to recommend that these become canonical. But having recently observed what happened when the old-fashioned non-XML method of math typesetting was supported by WordPress.com, I have to ask: How much more mileage might we be getting out of the existing print-oriented systems?

I am not an expert user of PDF authoring tools, nor an expert user of software libraries that enable programmatic manipulation of PDF files. But some of you are. What would it take, I wonder, to post-process the kinds of PDF files that governments typically produce, in order to add Purple Numbers?