Slight shifts will occur between the printing, trimming and scoring processes, meaning a perfect registration of the printed artwork to any fold lines in your saddle stitched booklet will not be possible. We recommend to factor this into your design by keeping artwork away from the folded lines by 0.125 inches, or by placing the artwork across the folded line purposefully, so any small shift will not be noticed.
It is not mandatory to keep your text and images away from the folded lines, however you will likely see some portion or all of your order showing shifts similar to the following reference images, which would not qualify for a reprint.
On the outside cover, this shift may appear as artwork overlapping the spine and shifting slightly onto the other cover.
This shift does not only occur on the outside cover - it can also cause mis-registered artwork to appear along the centre seam inside the booklet. Since saddle-stitched booklets are created from larger sheets folded in half to create pages, you might see part of the shifted artwork showing up on a different spread than intended. Please see the image below for further reference of how the artwork placed close to the seam can become split between different spreads within the assembled final product. By keeping your artwork away from the inside seam by 0.125 inches, you can avoid this effect from occurring in your booklet.