I am very impressed with the significant amount of due diligence you've done here trying to sort this out. It reminds me of me in my early days.

You are exceptionally articulate, detailed (yet quite concise), big-picture/long-term thinking and respective of prior art. This is very impressive.

My gut says that with all the thought that went into just figuring out if you should extend a current namespace, you should come up with your own (under "PDF"), that doesn't include any acronyms that aren't particular to your distribution. I also think that you should request MAINT access to the existing distribution; not necessarily for updating it, but perhaps to update the README so that it claims the old software as either A: deprecated (because your software is backward compatible) or B: antiquated (because your software does *most* of what the older one does, but maybe not everything), either/or with a link to your distribution.

I stood on my head for my first couple of CPAN releases, waiting for feedback from others on how I should proceed. I was scared shitless. I was afraid of infringing on other's distribution names, their work, and perhaps mostly, breaching the conduct of creating a new CPAN name for my work.

Don't overthink it. You've worked overtime to ensure you're within the guidelines, and you've gotten wonderful feedback from many people.

Just do it. Get your distribution up there in what makes you feel best, and be very proud to be an official open source Perl CPAN contributor!

-stevieb