why would winston sometime need back issues of newspapers in his work?

Winston works at the Ministry of truth. The irony of this ministry resonates throughout the novel. Here the truth is fabricated and any historical references to the real truth is vaporised. Winston’s job is to track down traces of vaporised people written in newspapers and destroy them. Winston also had to track down articles that did not correspond with the Party's forecasts, predictions, news of the day..... and destroy them as well. Winston had to bend, twist and destroy history to recreate the reality of Oceania.