Go to 'Layout' > 'Size' > 'More Paper Sizes' and input the custom 841x594 mm dimensions.
If the design features images reaching the edge, add a 3mm bleed, resulting in a final setup size of postery formata a1 skachat
Save your finalized poster as a PDF for the best printing compatibility. Creating A1 Posters in Common Software Go to 'Layout' > 'Size' > 'More Paper