it's simple, if you sold me the pdf version, don't come now and change what you sold me. If i would pay it monthly would not be problem, i just dont buy it anymore, but you sold a complete year subscription so keep your word and give what you sold.
Im not saying that is a good or bad measure...there would be diferent opinions...what im sayin is that I pay for a PDF version not otherwise, so isnt correct you change it now after ive payed.