Layout - Symmetry
The more visually appealing your poster is, the more likely that your audience will be attracted to it and will read it. Symmetrical designs are visually pleasing and will give your poster a sense of balance.
Keep in mind that when designing a poster, symmetry of the title or horizontal top area does not necessarily need to be symmetrical with the content. Also, perfect symmetry is not always required to ensure a sense of balance, but the largest elements or the majority of elements should be symmetrical.
Horizontal Symmetry - when the poster content is divided on a horizontal line, the top and bottom mirror each other:
Poster Layout - Horizontal Symmetry
Vertical Symmetry - when the poster content is divided on a vertical line, the left and right mirror each other:
Poster Layout - Vertical Symmetry
Diagonal Symmetry - when the poster content is divided on a diagonal line, each corner mirrors the other:
Poster Layout - Diagonal Symmetry