"When I saw the movie cut together, I realized this is a film that says something about -- about hope for the hopeless," said Williams.
The decade saw hits from Williams like "Rainbow Connection" and "We've Only Just Begun." He even won an Oscar with Barbra Streisand for the song "Evergreen" from "A Star is Born."
"I went from being different to being special," said Williams. "Being different is hard; being special is addictive. I mean, I was -- I became a lot better at showing off than showing up. If you put up a camera and a couch, Paul Williams was on it. And I loved it."
He was everywhere. But success turned to excess as Williams turned to drugs and alcohol. He's been clean for 22 years now, but he knows the toll it took.
"I had to get sober. It was get sober or die," he said. "When I got sober, the career I thought I had had been gone for a decade."
When filmmaker Stephen Kessler realized his idol was still alive, he approached him about making the documentary. He ended up working on the project for more than four years.
"Paul says we went from stalker to brother. Of course, I don't think of myself as a stalker. I think of myself as a fan who wanted to do something wonderful for him," said Kessler.
At first, Williams was weary of the idea.
'When this gentleman came to me and said, 'I want to make a film about your life back in those days,' you know, there's nothing more pathetic -- there's nothing more pathetic than some little old man saying, 'Please, sir, may I have another cup of fame.' It's just -- it's just disgusting. And it's not who I am," said Williams.
But fame is no longer important to him. Today, he's busy writing more music and working on a children's musical with his wife.
There are also his duties as president of the American Society of Composers, Authors and Publishers, or ASCAP. He considers that his greatest honor.
"The greatest gift to a songwriter is to have what I call heart payment," said Williams. "Somebody comes up and says, 'You know what, Mr. Williams? My mother was a single mom and 'You and Me Against the World' was important to her.' Or, 'We got married to 'We've Only Just Begun' or 'Evergreen.' or 'Rainbow Connection'...[It's] as good as it gets for a songwriter."
"Paul Williams Still Alive" is in theatres now.