After graduating from Temple University, Paul taught in Philadelphia inner-city Christian schools for ten years. For the first three years he taught middle school in an all-black school. Then, with a group of parents, he started Spruce Hill Christian School (K-8), an inner city, multi-racial school. For seven years he was principal and teacher.

In 1983 he began working with his father, Dr. Jack Miller, on what became World Harvest Mission. World Harvest has teams serving in nine countries. He was Associate Director of the mission from its beginning in 1983 until 1996--he was responsible for operations, field expansion, and renewal ministries. From 1997 to 1999 he completed a Master of Divinity at Biblical Theological Seminary.

During his time as Associate Director he wrote several discipling courses. From 1985-88 he designed and wrote a course on grace called Sonship, which is popular in the Presbyterian Church of America. In 1989, he wrote Discipling by Grace, a companion course to Sonship. Both of these manuals have since been updated and re-written for World Harvest. These two manuals and their tapes have a worldwide distribution. In the early 90s Paul also wrote The Love Course, a course that studies the personality of Jesus as a way of learning to love. It is the precursor to The Person of Jesus course.

Paul is married to Jill, who is known for her sense of humor and faith. They have six children and three grandchildren. Their oldest two children are married. Their fourth child, Kim, is disabled. Paul and Jill were charter members of New Life Church (Glenside, PA), where they attended for 23 years before they moved for Kim's schooling. Paul was a deacon, co-coordinator of the deacons and then an elder at New Life, while Jill taught Sunday School almost continuously. Currently, they both regularly attend Line Lexington Church (Hilltown, PA).