This U.S. industry comprises establishments primarily engaged in converting paper and paperboard into products used for writing and similar applications (e.g., looseleaf fillers, notebooks, pads, stationery, tablets). Cross-References. Establishments primarily engaged in-- ? Manufacturing envelopes--are classified in U.S. Industry 322232, Envelope Manufacturing; and ? Manufacturing die-cut paper and paperboard office supplies--are classified in U.S. Industry 322231, Die-Cut Paper and Paperboard Office Supplies Manufacturing.