File format, scale and resolution
PDF is the preferred delivery format. Prepare the document at final size whenever possible. Very large graphics may be supplied at a clearly stated reduced scale, for example 1:10, but every dimension and resolution value must follow the same scale. Do not stretch a small bitmap to banner size and assume that exporting it as PDF will improve its quality.
The required resolution depends on viewing distance. A poster viewed from close range needs more detail than a banner installed high on a building. Logos, icons and text should preferably remain as vectors. Photographs should be checked at the effective size used in the final layout.