I think it is still possible to translate 抄紙 as " papermaking" in this context, because, while 抄紙 really does indicate a part of the process of making paper, this part (抄紙し) is about making paper as well: first, the paper is made (抄紙し), then, still wet, it is spread in several layers (複数の湿紙を抄き合わせ) and then multi-layered (or maybe simply thicker) paper is produced (多層抄き紙を製造する紙). The sentence itself explains that what is understood by "papermaking" (抄紙) here (in this document, in this paragraph or in this particular clause, perhaps) is the process of producing multi-layered paper, not just any paper, and in a specific way. Still, in order to produce that multi-layered paper, first the paper to create those layers must be made. Basically, papermaking remains papermaking regardless of the number of the layers the paper will eventually have.