in conjunction with my War on the Bluebook, I've made a prototype of a demonstration project proving that you can just embed machine-readable citation files directly into a PDF. (Also, finally proving that I hate the bluebook more than I hate writing javascript).
To run on your own, just spin up a local webserver. This runs in pure client-side javascript, no server required.
Available live at https://gowder.io/citations/ . Tested and works in chrome on desktop, no clue about other platforms.
This repo also contains two dependencies for this project, Coherent PDF and a Base64 library by Dan Kogai. The former is under the AGPL-3.0 license, and the latter is under the BSD 3-Clause license. Please see the above links for license details, source code, etc. It also uses Skeleton for CSS. It attempts to embed Raleway font from google fonts, but that doesn't seem to be working and, frankly, I don't care enough to fix it.
update: coherentpdf broke. now uses PDF-lib which is licensed under the MIT license. No longer uses coherentpdf at all (though I did adapt some of their example code)
note to self: dev build/server: npx parcel index.htmlbuild for prod npx parcel build index.html --public-url ./ (the last thing is to force it to use relative urls for the javascript and css files)