Paulist Press is an established press that has been around for 150 years. It is founded and run by the Paulist Fathers, a society of missionary priests founded for and by Americans in 1858. Paulist Press publishes Christian books in a wide variety of sub-genres, they have excellent distribution and sales within that market. They primary publish print books but they also publish electronically as well. They do not publish fiction except for children’s fiction.
To get a good idea of what they publish it can be helpful to review their bestsellers list or browse their new releases.
They have four separate submission guidelines for the four primary categories of books that they publish: Academic Books, Children’s Books, Popular Books, Professional or Clergy Books. They publish four types of Children’s books: Picture books, Activity books, Chapter books, and Prayer books.
When they refer to popular books they mean ones aimed at a lay (not clergy) audience.
All of the guidelines are very specific and you should read the ones for your category closely and make sure that your proposal matches their requirements. Submissions for all categories should be made through the same email address. Electronic submissions are preferred but submissions are still accepted through the mail.
Proposals for all categories can be made before the manuscript is complete.
To learn more about their submission guidelines visit their website here.