PORTLAND — MaineToday Media CEO Richard L. Connor announced his resignation from the company Friday and will step down on Dec. 31.

Dale Duncan, MaineToday president since July, also resigned, effective Friday.

MaineToday, which owns The Portland Press Herald/Maine Sunday Telegram, The Kennebec Journal in Augusta, the Morning Sentinel in Waterville and the Coastal Journal, will be managed by an interim team during the search for Connor’s successor.

In the media release, Connor said he “led a significant transformation of this company.”

He noted that MaineToday recently reported the first increase in paid circulation in five years, and that the Maine Press Association named the Portland Press Herald the Best Daily Newspaper in Maine two weeks ago. In addition, Connor said, the company revamped its websites and online products and launched the MaineToday Digital division two months ago.

“Now the company needs to leverage the new foundation into the next phase,” he said. “After four years of work with a schedule that has been around the clock … it’s time for change for me personally, my family, and for the company. I remain a significant individual investor in the company and I believe in its future.”

Peter Brodsky, MaineToday Media board chair, said in the statement that the board will immediately begin seeking Connor’s successor.

“We will be recruiting leadership for these properties with strong ties to emerging media technologies that continue to shape the future of this industry. Rich Connor’s long experience in the newspaper industry provided a critical start to the reshaping of these newspapers,” Brodsky said. “Future management will build on that foundation. MaineToday Media looks forward to continuing its role as the leading source of news and quality journalism in Maine.”

Brodsky is a former employee at Dallas-based HM Capital Partners, a major MaineToday investor.

Connor said he will assist with the leadership transition in coming months.

Scott Wasser, Portland Press Herald/Maine Sunday Telegram executive editor, said he will miss Connor’s leadership.

“I told the newsroom when I first got here two-and-a-half years ago that Rich was the best boss I ever had. That never changed,” he said. “We will continue to do the great journalism that (Connor) brought here.”

Portland Newspaper Guild president Tom Bell said in a letter to members that Connor improved the paper’s quality and community relations and stabilized circulation.

“But that is not enough. We must build on that success and deliver news and services on platforms other than newspapers, and we now need a digital-savvy leader who can take us to the next level,” said Bell, adding that the union will soon finish negotiating a new contract.

“The union is committed to helping the company remain successful. At this time of transition and uncertainty, we must be flexible, but our strength and commitment is also a source of stability for our readers and advertisers, our company and our workforce,” he said.

An investment group led by Connor, a Bangor native, bought the company in June 2009 from Seattle Times Co.

Since then, the company centralized printing, moved to new offices and, weeks ago, announced a restructuring that included 38 layoffs and voluntary severance of 23 employees.

Former Maine Governor John Baldacci praised Connor for keeping the Portland Press Herald “an independent Maine paper, not part of a national franchise.”

“I think he stabilized (the company in) a very difficult economy and during a challenging time in the newspaper business,” Baldacci said.

Alan Baker, owner and publisher of Bar Harbor’s Mount Desert Islander and The Ellsworth American, called Connor a “breath of fresh air” for the Portland Press Herald.

“I thought he was good for the Maine newspaper industry because he turned the (Portland Press Herald) around. Most people I know think the paper is much more interesting under his leadership,” Baker said. “I don’t know anyone in this industry that has worked as hard as he worked in the last three or four years.”

Chris Hall, senior vice president of the Portland Regional Chamber, said he was “surprised and saddened” by the departure of Connor, a “very generous supporter” of the chamber.

Connor also sits on the board of the affiliated Portland Community Chamber.

Hall recalled a speech Connor made about media challenges at a September 2009 event.

“He was taking up a challenge many people weren’t sure he could meet,” Hall said. “Much to peoples’ happiness, we still have a paper, and I give him credit for stepping up and being a leader.”

Former President Duncan said he resigned because the “owners want new leadership.”

Duncan, who is former publisher of The Indianapolis Star and joined MaineToday in 2010 as a contractor, said he enjoyed his time with the company, particularly overseeing 2010 election coverage. He also praised the professionals at the company, including Kennebec Journal and Morning Sentinel staff.

Duncan described the four months as president as a challenge. In that time the company launched MaineToday Digital, hired a new chief financial officer and cut expenses during a difficult revenue environment.

“The organization responded well,” Duncan said. “And because of the steps we made in the last six months, the organization will be fine in the near term while it deals with a rapidly changing business model.”