“Alles” in German does double duty as a pronoun meaning “everything”, so the “it” is required to accompany all, which is otherwise an adjective. Now, “all” can also be a pronoun in English, but it's usage is different and it doesn't work very well as a pronoun in this situation. So, you either translate “alles” as “it all” or (as is more common) as “everything”.
I guess both are in principle, assuming you are using "you all" to indicate a group of people. Have you read everything is just the more accurate translation, the 'you' meaning multiple people. There's no 'it' expressively given in the German but using "it all" should convey the same meaning as everything.