Turning off cutting lines will remove the printed cutting lines, so you are left with seam lines only. This leaves you with a basic block of the pattern, and is helpful if you plan to make pattern adjustments or change the seam or hem allowances. Turning off seam lines will remove the printed stitching lines from the pattern. This is helpful if you do not plan to make adjustments to the pattern and want to see the cutting lines only. It will reduce visual clutter on your printed pattern which makes cutting easier, especially if you plan to print multiple nested sizes at once.