The report on the Altoona-Johnstown Diocese was based partly on evidence from a secret diocesan archive uncovered through a search warrant executed last year, said Pennsylvania Attorney General Kathleen Kane.
"These predators desecrated a sacred trust and preyed upon their victims in the very places where they should have felt most safe," Kane said in a statement.
No criminal charges are being filed because some abusers have died, the statute of limitations has expired and, in some cases, victims are too traumatized to testify, she said.
The report said Hogan covered up abuse allegations by transferring offending priests, including by sending one accused clergyman to a school for boys. It said Adamec or his staff threatened some alleged victims with excommunication.
One diocesan official under Hogan, Monsignor Philip Saylor, told the grand jury that church officials held such sway that "the police and civil authorities would often defer to the diocese" when priests were accused of abuse, the report said.