Because these PDFs are publicly/freely available, it could be undertaken to convert them to mobi and ePub formats (if one were so inclined). Maybe see if existing free ebook processors [1] [2] would accept these into their pipelines?

Heck, the US gov even has a service to do this for departments who pay for it [3].

[1] https://www.pgdp.net/

[2] https://www.gitenberg.org/updates

[3] https://www.gpo.gov/how-to-work-with-us/agency/services-for-...