The women were targeted because they needed help with child custody cases or criminal charges, prosecutors said. Some had struggled with drug use or were survivors of sexual abuse.

But once Chad M. Salsman had guided the women into his private law office, ostensibly to discuss their cases, he forced them onto his desk and sexually assaulted them, prosecutors said. He then told the women not to tell anyone what had happened.

Mr. Salsman, who was a practicing defense lawyer at the time, went on to win election as the district attorney of Bradford County, Pa., in 2019.

But his pattern of predatory behavior was not publicly known until he was arrested on Wednesday and charged with more than a dozen crimes, including sexual assault, indecent assault and intimidation of a witness or victim, prosecutors said.

Josh Shapiro, Pennsylvania’s attorney general, said the charges reflected crimes against five women over the past several years, although he said that his office knew of additional victims whose cases could not be prosecuted because the crimes had occurred too long ago under the statute of limitations.

“The details of these assaults are incredibly disturbing, and they are criminal,” Mr. Shapiro said at a news conference in Bradford County, a rural part of Pennsylvania about 65 miles northwest of Scranton, along the New York State line.

“Mr. Salsman abused his position of authority as a lawyer and as a public official here in this county,” Mr. Shapiro said. “The victims in this case were relying on him to be their advocate, to represent them at a time when they felt powerless, and instead they ended up being preyed upon.”

Mr. Salsman, 44, pleaded not guilty and plans to fight the charges, his lawyer, Samuel Stretton, said.

Mr. Salsman has rejected calls to resign, although he has handed over the day-to-day handling of cases to his first assistant district attorney, Mr. Stretton said.

“He has denied any misconduct,” Mr. Stretton said. “There was never any nonconsensual sex. There was never any inappropriate touching. It’s just not true, and we have adequate corroboration to prove that.”

Mr. Salsman began practicing law in 2001 and won a contested race as a Republican in 2019 to replace the district attorney, who was retiring. He said that his three daughters had inspired him to run and that he hoped to rid the county of its reputation as “Meth Valley.”

“I want both my family and yours to feel safe living in Bradford County,” he told The Morning Times of Sayre, Pa., in October 2019. “I will be a tough but fair district attorney who always seeks justice for crime victims while protecting our constitutional rights.”

But even before he took office in January 2020, Mr. Salsman was already under investigation, according to court records, which show that the case had been referred to the Pennsylvania attorney general’s office in late 2019 by Mr. Salsman’s predecessor as district attorney, Daniel Barrett.

The investigation found that Mr. Salsman had a pattern of advances, coercion and assault against female clients who were in vulnerable legal or personal situations, Mr. Shapiro said.

Mr. Salsman would begin by asking the women for explicit photos or groping them in court or in private meetings, Mr. Shapiro said. When the women said they were struggling financially, Mr. Salsman pressured them into sex instead of charging them legal fees, Mr. Shapiro said.

After assaulting the women, Mr. Salsman directed them to a small bathroom in his office to clean up with paper towels or wipes, Mr. Shapiro said.

Staff members at Mr. Salsman’s law office told a grand jury that he asked his secretaries play music or run a noise machine or an air-conditioner during client meetings. The staff members said they often saw women leave the office in tears, Mr. Shapiro said, adding that Mr. Salsman had told victims he could “ruin their lives” if they spoke out.

Most of the misconduct charged in the case took place when Mr. Salsman was in private practice as a defense lawyer, although Mr. Shapiro said one assault had happened in November 2019, after Mr. Salsman had been elected district attorney but before he took office.

Mr. Shapiro said that Mr. Salsman had also continued to intimidate his victims after he was sworn in.

“Even during our office’s secret grand jury proceedings, while he was district attorney, Chad Salsman tried to pressure victims and members of his own staff to disclose what they had told the grand jury in these secret proceedings — a further attempt to scare them into silence, and an attempted corruption of the judicial process.”

Mr. Shapiro said that Mr. Salsman “chose these victims purposefully by design,” adding: “He thought they would be easy to silence and likely they would be less believed if they ever came forward. We’ve seen this playbook before.”

The Abuse and Rape Crisis Center of Bradford County called the charges “traumatizing and horrifying to our community” and said it believed there were probably more victims who had not come forward.

The center said on Facebook that Mr. Salsman’s law license should be revoked and that he must resign.

“While this case proceeds through the legal system,” it said, “there is a broken trust with the safety and integrity of the Bradford County District Attorney office that will not be healed while Salsman retains access to former, current and future victim files.”