For subsequent mounting, it is recommended to add in the file at least 6 mm per each side in addition to the final size (bleed). For very large formats, 8 mm bleed is recommended.
Example: If the final image size will be 40.0 cm x 60.0 cm (e.g. size of the Alu-Dibond plate) the print file must be at least 40.6 cm x 60.6 cm (print area). When framing in a passe-partout, an all-round white border of at least 15 mm is recommended.