The first thing to note is that this demo (the Acrobat plugin) is an application. And that comes with its own baggage, i.e. this is a Windows only plugin and is targeted at Acrobat Reader 8. On a wider purview the application merely bridges an identifier embedded in the media file and the handle record filed against that identifier and delivers some relevant functionality. The data (or metadata) declared in the PDF and in the associated handle if rich enough and structured openly can also be used by other applications. I think this is a key point worth bearing in mind, that the demo besides showing off new functionalities is also demonstrating how data (or metadata) can be embedded at the respective endpoints (PDF, handle).
This is a companion discussion topic for the original entry at https://0-www-crossref-org.lib.rivier.edu/blog/handle-plugin-some-notes/