Over the course of a celebrated 40-year career, veteran Danish editor Niels Pagh Andersen has worked on critically acclaimed films including Pirjo Honkasalo’s “The 3 Rooms of Melancholia” and Joshua Oppenheimer’s Oscar-nominated “The Act of Killing” and “The Look of Silence.”

One of the key takeaways from those collaborations, which he explores in his new book “Order in Chaos: Storytelling and Editing in Documentary Film,” is the importance of the creative synergy that forms between an editor and a filmmaker.

“The artistic vision is the director’s responsibility. But with the [editing] process, there I feel it’s also my responsibility that we get the best out of the two of us,” says Andersen, who gave a masterclass this week at the Thessaloniki Documentary Festival. “If you can have the creative dialogue, then you create something that is bigger than the individual.”

In “Order in Chaos,” Andersen offers readers a look into the principles and methods behind his creative process through case studies of eight films that he edited, including Oppenheimer’s two Academy Award-nominated features, Jennifer Fox’s “Flying: Confessions of a Free Woman,” and Ai Weiwei’s migration doc “Human Flow.”

The e-book version includes exclusive clips from each of the movies, as well as conversations with the directors, offering a rare behind-the-scenes look at the creative process behind some of the most significant documentary films of recent memory.

Andersen got his start in the 1970s under the tutelage of Christian Hartkopp, one of the leading Danish editors at the time. His breakthrough came with an offer to work on “Pathfinder,” from Norwegian director Nils Gaup, the first feature-length film to be shot in the indigenous Sami language. The Dane boarded a flight to Norway without so much as reading the script.

The leap of faith paid off when the movie earned an Academy Award nomination for best foreign-language feature. “That film became a huge success,” says Andersen. “It opened so many doors.”

The newfound success marked a dramatic shift for someone who until that point had been a “young nobody,” as Andersen describes himself at the time. After a battle with alcohol addiction that almost cost him his career, the Dane found a “second life” editing documentary films, discovering a community “who wanted to tell the world something and also had a deep interest in the world.”

Andersen brings his own curiosity to the table with each new documentary he edits. “When I start on a film, [I treat it as if] this is the first film that I ever edited,” he says. “Every documentary film develops its own language while we are editing…[and] what is so important for me is that I take in the material and see what is the uniqueness of that material.”

Though he learned his craft in the editing room, Andersen now teaches at the Norwegian Film School, something that he credits with bringing a fresh perspective to his work. “That was very important to me, because suddenly I had to develop a language of what I was doing,” he says. “I became much more conscience of what I was doing as an editor, and therefore I was also able to develop myself as an editor. I was learning by teaching.”

Appearing in conversation last year with IDFA artistic director Orwa Nyrabia, Andersen pointed to some of the high points of his career and described his work as a “learning process” that continues to shape him both personally and creatively.

“I have been so privileged that I met at the right moment Pirjo Honkasalo and her project ‘3 Rooms of Melancholia,’” he said. “That’s where a new thing started for me, and later, of course, ‘The Act of Killing’ was something I had never tried before, on all levels. I was lucky to find the right project which pushed me somewhere else. And I can say about myself that I’m curious and I’m not afraid.”