Unfortunately while the colorsync trick does work to allow selection and copying, whatever way the pdfs are encoded I end up with mojibake for everything including the English.
It's not a system issue as I can copy and paste perfectly well from other pdfs for instance The Daily Yomiuri's Pera Pera Penguin column.
I don't think JapanesePod want to specifically prevent copying. (I could be wrong) I think it's a by-product of how they generate their pdfs. Perhaps they are this way so they can be viewed on systems without Japanese fonts installed.
They should really investigate it and make them a bit more user accessible.
Or if their policy is that users shouldn't copy and paste out of the pdfs. (eg.for word lists ) it might be worth stating that as well.