It depends on what belt model you select.
Thick Core / Stiff Belts feature "integrated embroidery": we embroider the fabric first and then we make the belt. There will be no trail on the reverse side, but the belt stitch lines will be over the embroidery.
Soft Belts come with "non-integrated embroidery": we add custom embroideries to the finished belt. The embroidery will be over the belt stitch lines but the reverse side will show a trail.
You can find this information in the belt specs in the product page.