First of all, I don't know if this is not a place for asking this question or whether it has been asked (I have searched before posting). My apology is these cases.
I felt very often to save all discussions (including answers) about a question permanently in my computer. Thats why the question. I have seen many journals (e.g., Nature) have an option "download pdf", while seeing the article in their site. It would be great, if this facility can be made available.