Church officials discovered the papers last week during a review of another priest's records, said the Rev. Christopher Coyne, an archdiocese spokesman.
They were given to lawyers for Gregory Ford, 24, and his parents, who are suing Cardinal Bernard Law and the archdiocese for allegedly failing to protect Ford from abuse by the Rev. Paul Shanley.
The lawyers released the papers later Thursday.
In excerpts of what Attorney Roderick MacLeish described as Shanley's writings from 1972, the priest describes in frank language his life as a "street priest," ministering to drug addicts, runaways and homosexuals.
The writings also refer to his own experiences with venereal disease.
The papers also show the archdiocese ignored warnings of Shanley's involvement with the North American Man Boy Love Association, which endorses sex between men and boys.
MacLeish said he received about 800 pages. Coyne said many were believed to be duplicates of the previously released documents.
The archdiocese had previously released about 800 pages of church records.
Those documents showed church officials had been told of allegations of abuse against Shanley as early as 1967; they would eventually receive a total of 26 abuse complaints. Shanley was never charged in any of those cases.
Also included were articles showing the archdiocese knew Shanley had been a vocal proponent of sex between men and boys, as well as correspondence between the archdiocese and the Vatican on Shanley's views about sex.
Shanley, whose last known address is in San Diego, has issued no public statements since the case began.
Coyne said the discovery of the new documents, which included letters reporting that Shanley approved of man-boy sex, is more evidence that officials received and ignored numerous complaints about Shanley.
"It's terribly embarrassing at this late date to come out and say this," Coyne said. "No one knew these files were around. It wasn't just one letter that was overlooked. It's another bad thing. It makes us look like we're not being honest."
In other recent developments:
The Philadelphia Archdiocese Friday night hosts an annual fundraising dinner with eight cardinals in attendance. Most years, the event raises about a million dollars for Catholic University.
Keeler Thursday created a new office to review sex abuse policies in his own diocese; a priest is heading up the panel.