additional printing after the main print
Technical printing term: applying an extra ink (often a spot color or varnish) after the main CMYK process. Used in commercial printing contexts.
このパッケージは、特色を後刷りで加えています。
This package has a spot color added by additional printing after the main print.
Compound of 後 (あと, 'after') and 刷り (ずり, 'printing', the continuative form of 刷る). Literally 'after-printing'.