How to read philosophy digitally

I want to start reading philosophy, but I don't want to buy the physical books all of the time because I don't have the money for buying hundreds and hundreds of books and given that most philosophy books are in the public domain I can just download the pdf's for free. This is where I'm having a problem though, as I can't find any good apps for reading. I want to be able to annotate and highlight/underline. I don't care if its a payed option. I don't mind if I have to use multiple apps btw. Oh and If you think it's necessary for me to read physical books then I will buy them, it's just that I would prefer to not spend too much :(