The pdfs of these for sale by
WotC are watermarked, not sure how easy it is to remove that, but if those are not present, maybe one can assume that it is the
POD version, purchased legitimately. (That is giving the seller all benefit of the doubt). That would be ok to resell
IMO.
Not worth $40 though, you can get both a
POD and pdf from drivethrurpg for probably less than half that price.