What are the margins required when designing files for Perfect Binding?

The general margins for booklets is a minimum of .25" or 1/4" on all edges. However, an additional margin of .25" or 1/4" should be allowed on the spine edge (for a total of .5" or 1/2"). This includes space for the glue itself as well as margin to ensure that no content "falls" into the spine and becomes difficult to read or obscured.