What about any of the ways to convert epub to pdf yourself? Are they no good?
If anything, I think an HTML version that you can view right on the website would be the best format addition. It's always interesting to me when a website doesn't offer a browser-native document format as an option to view text.
I've tried generating PDFs with Calibre, the result: giant ugly fonts, zero sheet padding, nonsensical spacing, etc.
I could spend the time trying to make them look right, but I don't want to spend my time that way. I prefer learning things that will give me more satisfaction per second spent.
If anything, I think an HTML version that you can view right on the website would be the best format addition. It's always interesting to me when a website doesn't offer a browser-native document format as an option to view text.