I work for a company that sends out about 500 statements to customers. Each statements varies from 9 to 15 pages. Statements come out printed in a collated form. I am required to select only the pages that refer to each customer , and place them to an envelope and seal it afterwards. The problem is that this often leads to statements that refer to two customers being mistakenly placed into one envelope. How can I avoid this error? Is there a way to do it?