In order to see the critical tasks in your project, go to Gantt Chart view and in the Project tab click on the Critical Path button. All the critical tasks become red in the Gantt Chart.

To filter all the critical tasks in your project, go to Project ribbon – Filter and select Critical.

After this, you can Print in A3 format these tasks by going to menu File-Print-Page Setup and export the project in a A3 format.