Thousands of pages of documents showing how the Archdiocese of Chicago handled the sexual abuse of children by priests are to be made public, providing the broadest look yet into the details of what the church knew and did – or didn't do – about the scandal.

Last week the archdiocese – one of the largest and most influential in the US – handed over more than 6,000 pages of documents to victims' lawyers, who said they would show that the archdiocese concealed abuse for decades, including moving priests to new parishes where they molested again.

The disclosures involving 30 priests were made as part of legal settlements with abuse victims, and are similar to disclosures made in other dioceses in the US in recent years that showed how the Roman Catholic church shielded priests and failed for many years to report child sex abuse to authorities.

Chicago officials said most of the abuse occurred before 1988 and none after 1996.

Cardinal Francis George, who has led the archdiocese since 1997, released a letter to parishioners on 12 January in which he apologised for the abuse and said releasing the records "raises transparency to a new level". He stressed that much of the abuse occurred decades ago, before he became archbishop. He said all of the incidents were eventually reported to civil authorities and resulted in settlements with victims.

"I apologise to all those who have been harmed by these crimes and this scandal, the victims themselves, most certainly, but also rank-and-file Catholics who have been shamed by the actions of some priests and bishops," George wrote.

The archdiocese has paid millions of dollars to settle sexual abuse claims, including those against Father Daniel McCormack, who was sentenced to five years in prison after pleading guilty in 2007 to abusing five children while he was parish priest at St Agatha Catholic church and a teacher at a Catholic school. The next year, the archdiocese agreed to pay $12.6m (£7.7m) to 16 victims of sexual abuse by priests, including McCormack.

Files on McCormack will not be among those released on Monday; they have been sealed by a judge because of pending court cases, Pearlman said. He said he and St Paul, Minnesota, lawyer Jeff Anderson would re-release the McCormack documents that they had.

Many of the accused priests are dead, and the documents will include only 30 of 65 priests for whom the archdiocese says it has credible allegations of abuse.

Peter Isely, Midwest director for the Survivors Network of those Abused by Priests, said it was important for all Chicago-area Catholics to read the documents.

"This is about a part of their story as Chicago Catholics that … has been systematically hidden," Isely said.