In this particular branch of publishing, I recorded a podcast with a self pub author. He had two books out: A and B. A had 20 times the sales of B. Sales were rock solid steady year round. And then A was pirated - sales of A dropped to about half that of B, and again, they are both steady at that rate.
This particular author said, in the podcast, he can't put out another book because all the editors, graphic artists and layout people won't do their jobs unless they are paid in advance. And he can't afford the risk of paying them and never getting that money back. So this six new books he was working on have been shelved. And it is my opinion that his work is genius.
Maybe in the world of software engineering publishing the sales lost to piracy are negligible. But the same cannot be said for all books.
So not only do I have a position that is different from yours, but even if I shared your position, I would not get enough air time to say anything. "If somebody bought by book on your site would they just get the pdf?" "Yes." "No thanks."
The authors are okay with kindle. The user can view it online, or download the book - but doesn't get a file they can share.
So I am asking here to look for actual software engineering solutions.
I guess I thought there would be a service called Bindle. And they would offer apps on a bunch of platforms. And they would have an API. I would pay them something like $400 per year and I could say "for this PDF, I want it to only appear on my website. And allow the user to download, but only in a format readable by the Bindle offline reader."