It's clear the witness needs the document to answer the prosecutor's question, so what's the value in the prosecutor asking the witness the question the first time without the document?
In a court room, most actions taken by the attorney are for one reason and one reason only: To convince the Jury to give them a favorable ruling.
The example you cited is likely part of an attempt by the attorney to impeach a witness during cross examination (it should be noted that impeach here means something different than the commonly understood meaning of the term. Here, it's an informal process of convincing the jury to discount the testimony of the witness by demonstrating that they're testimony is unreliable. Because U.S. courts are adversarial, the opposing attorney will try to poke holes in the testimony of the witness during cross-examination.).
As to why the Lawyer even asked the question in the first place if he knew the answer, especially during cross-examination, it's to get the witness to contradict themselves out loud before they introduce the evidence. But then, the fact that you spotted one instance of a lawyer knowing what the answer is before they ask the question, that's their big secret... a good attorney knows the answer to every question they ask in court before they ask it.
As a juror, you didn't see the work the lawyers on both sides did... each one took statements from their witnesses, and formed questions with them and coached them on the proper way to respond (this isn't necessarily what to say... but how to say and who to say it to... if you are ever called as a witness, the attorney who coaches you will make sure to tell you when you answer a question on the stand, look at the Jury (or Judge in a bench trial) when you respond and not the attorney who asked the question... because people tend to believe that when someone doesn't look at them they are lying) to the questions and what to say on cross to avoid legal trouble. And then, they get to interview the witnesses the other side is bringing in to testify (in fact, if a witness for the opposing side refuses to talk to your lawyers prior to trial, that fact can be introduced in court to show the witness is not to be trusted, since the discovery phase of the trial has some broad rules that allow both sides to investigate the others case.).
In this particular case, the witness being question testifies they do not know ("I don't know/recall" or similar statements are frequently used to avoid perjuring one's self when contradictory evidence is introduced... while it could be a lie, it's hard for a prosecutor to prove if you were faking the lack of knowledge or if you really forgot. If you say no and it turns out that you should have known that no was the wrong answer, it's easier to get perjury charges.). Upon this, the cross-examining attorney, knowing the answer, has the document ready to go and can point to the line and have the witness read the answer for the court (or as I was taught by an attorney coach on my mock trial team, the better way is for the attorney to hand a copy of the doc to the witness and say "Please read along as I read out loud..." and then read the part of the document that is relevant. This is so the witness can't try to recover by reading it in a favorable tone or read parts you might not want read.).
In criminal law, this is important for both sides. If the Defense can make you believe a prosecution attorney is unreliable... then what does that say about other elements of the case? If in doubt, you must acquit. For the prosecution, if the defense witnesses look reliable, there is doubt to the veracity of your case... and in order for you to win, the jury must not have any doubt you got it right.