In 1916 the name of the company was changed from the Nashua Card Gummed & Coated Paper Company to the Nashua Gummed & Coated Paper Company. World War I resulted in increased business for the company and necessitated improvements in the handling of colors in the Coating Division, additional storage space and a larger loading platform adjoining the railroad track. As a result, a wooden monitor was constructed on top of the west end of the mill for a mixing room to allow the colors to be mixed there and then flow by gravity to the coating machine floor. The upper level of the penthouse served as the laboratory for the chemist. At the same time a covered shipping platform was constructed. In 1913 the mill building was extended to the east and another storehouse was constructed on the south elevation. Charles T. Main again served as engineer for the additions.

After World War I, the company opened a subsidiary in Canada, the Canadian Nashua Paper Company, to avoid the high trade tariffs. In 1921 the company expanded into another important product line with the purchase of National Binding Company of New York and the manufacture of packing and adhesive tape. It was this kind of diversification as well as streamlining efforts that cushioned the company from the negative effects of the Depression felt by other local companies in the 1930s.

In 1937 additional large improvements were made to the physical plant with the construction of a four-story reinforced concrete and brick veneered addition containing 75,000 square feet at the east end of the complex. The building was intended to provide facilities for the newly established printed cellophane business and for storage. It was constructed by the Morton C. Tuttle Company of Boston. At the same time a modern administration building was erected west of the main structure (44 Franklin Street). News of the additions was praised in the local newspaper which stated "Since its location here shortly after the turn of the century the company has given unusually steady employment to a considerable share of Nashua's wage workers and is rightfully listed as one of Nashua's back-bone industries" (Telegraph, May 8, 1937).