A0 Posters are the ideal size for conference or presentation posters, as they are big enough to allow you to put a wide range of information on them which will be visible from a fair distance. A3 is a paper size that is typically used for drawings, diagrams and large tables. A3 Poster is the initial stage of advertising. When it comes to marketing impact, the printed poster presents excellent opportunities for innovative design and attracting attention. The A series paper sizes are now in common use throughout the world. Although the A series of paper formats is the most popular, sometimes your project may call for something that falls outside these parameters.