Pythocles read physical copies, and constantly had them in his hands...
From the start of the Letter to Pythocles:
[84] CLEON brought me a letter from you in which you continue to express a kindly feeling towards me, which is a just return for my interest in you, and you attempt with some success to recall the arguments which lead to a life of blessedness. You ask me to send you a brief argument about the phenomena of the sky in a short sketch, that you may easily recall it to mind. For you say that what I have written in my other works is hard to remember, even though, as you state, you constantly have them in your hands. I was glad to receive your request and felt constrained to answer it by pleasant expectations for the future.
[85] Therefore, as I have finished all my other writings I now intend to accomplish your request, feeling that these arguments will be of value to many other persons as well, and especially to those who have but recently tasted the genuine inquiry into nature, and also to those who are involved too deeply in the business of some regular occupation. Therefore lay good hold on it, keep it in mind, and go through it all keenly, together with the rest which I sent in the small epitome to Herodotus.