No, what would prove it would be to take a picture of the front cover and back cover of tomorrows newspaper and say what the first story inside the newspaper will be.
Consider giving someone tomorrow's newspaper. It is loaded with information. It is only proof once the events and circumstances unfold, otherwise it is just ink and paper. That is to say that the actual value of it is being able to witness proof of information traveling backward 1 day.
The proof of it is limited to witnesses of the newspaper relative to the events and circumstances within a 24 hour period. And once tomorrow's newspaper is released, your 'pre-paper' is no longer proof of anything, but rather merely another newspaper.
Even if you went to the printing presses and editor of the newspaper and showed it to them before they could produce tomorrow's newspaper, it is still limited to witnesses working to make the newspaper. They could shut down their operation to show that they haven't yet produced it, that they stopped mid-operation with half the stories, but it is still open to a lot of questions regarding authenticity. It becomes a matter of who can not only witness the newspaper and all events of a day ahead, but also all who can witness the presses and events and circumstances thereof. Doing as such could effect things like causing tomorrow's newspaper to never get printed, which gets into paradoxical issues and multiple worldlines.
It basically amounts to how many people could be witness before the next day when tomorrow's edition is released. If you released it globally, if it went instantly viral to the whole world before the next day, it would change the events and thus create all sorts of other paradoxical issues.
There is a theory floating around some intellectual circles that the timeline will correct itself as to not allow paradoxes, or that there is only so much deviation that the timeline will allow.
It gets complicated.