Eight unions at The Bulletin voted today to accept about $5 million in wage cutbacks and other contract concessions, thus preventing the shutdown of the 134-year-old newspaper -- once America's largest afternoon daily.

Champagne corks popped and reporters hugged each other in The Bulletin's newsroom when word that the unions, representing 879 of the newspaper's 1,901 full-time employes, had agreed to go along with a management bail-out plan.

"Let's go back to reporting news instead of making news," said a jubilant N.S. Hayden, The Bulletin's publisher.

Craig Ammerman, the newspaper's executive editor, said a Monday edition would be published. He then held up a copy of a contingency plan that had been distributed in case of a shutdown and hollered, "Anybody got a match?"

Ammerman, who came to The Bulletin a year ago, said he thought management's plan to turn the paper around would work.

"It's not going to be easy, but I think we can make it," he said. "I think we'll give it our best shot."

Asked if the company's final proposal added up to the $4.9 million saving it had asked, Hayden replied: "There had been a lot of shuffling, but the figure is pretty close to $4.9 million."

Details of the package were not disclosed.

The last holdout of the unions was Local 16 of the Philadelphia Newspaper Union, which represents the paper's 176 pressmen. They were still casting ballots as a 5 p.m. deadline set by management passed.

Negotiators for the paper and the unions had held one last bargaining session earlier in the day to work out the final details of the concessions sought by management Aug. 3.

After that 90-minute meeting, the labor leaders went to their union halls to brief the membership so they could vote on the package.

Sunday's editions contained little to indicate that it might have been the paper's last day. In fact, it included the first installments of three new series.

A Bulletin collapse would have ended Philadelphia's position as the only major American city with four newspapers.

It also would have marked the third time this month that a major American daily has been forced to cease or sharply curtail publication because of red ink. On Aug. 7 The Washington Star ceased publication. And in New York, the Daily News said Friday it was shutting down its year-old afternoon edition on Aug. 28.

In announcing the possible end to the paper, Hayden said The Bulletin had lost $7.5 million in 1979, $13.4 million in 1980 and $10.3 million during the first six months of this year.

Besides seeking the contract concessions, Hayden also said the newspaper would lay off nonunion employes at a savings of $1.4 million. About 125 nonunion workers were laid off last year, and over the past five years The Bulletin's staff has been reduced by almost 500 people.