I don't think there is any documentation for this.
I usually query the PeopleTools metadata tables for finding out . Two main tables related to Permission lists are:
PSCLASSDEFN: Stores all Permission list definitions
PSAUTHITEM: Stores the pages to which each Permission list gives access
Join these tables to fin out the what each PL is doing. To filter out custom Permission lists , use LASTUPDOPRID ='PPLSOFT' clause.
Another interesting field in PSAUTHITEM is AUTHORIZEDACTIONS. You can use this field to find out the level of access a PL gives for each page .