The workers are perforating the paper for binding into booklets.

perforating 是动词 perforate 的现在分词形式。perforate 由前缀 per-（表示"完全、贯穿"）和词根 forare（拉丁语"穿孔"）组成，意思是"打孔、穿孔"，特指在材料上打出一系列规则排列的小孔。