The Stolen Plans Mystery (Ted Wilford #7), by Norvin Pallas (epub/Kindle/pdf)
Ted almost pushed the panic button when he heard that Mr. Sawyer had disappeared. He was the one on the newspaper who was responsible for getting all the papers scheduled and delivered to the right places.
He called his friend, Nelson, who was also at home from college for the Christmas holidays and, while solving the delivery problem, they got involved in more mysterious ones. There was a Christmas promotion contest in which "LULU," the electronic computer (newly installed in the office) was to decide the winner. Some plans were stolen, as well as merchandise, from the stores and even a Robin Hood Santa Claus got mixed up in the story. Ted also had to figure out how to get out of a locked meat freezer. There's lots of suspense and excitement, in addition to solid facts about the newspaper business.