SHARON, Mass. (AP) _ The warning to advertisers on the front page of The Sharon Advocate bears testimony to the success of the nickel newspaper - ''NOTICE - the deadline for every edition is when the paper is filled.''

The Sharon Advocate, at five cents a copy, is full of town mischief, history and advertisements.

There are so many ads that advertisers ply co-editor Esther Reeve, 75, with flowers in attempts to get more ad space. But the newspaper won't get any bigger, say its owners.

''Sometimes, making money isn't the goal,'' said Walter Reeve, 79, who hasn't changed the price or missed an edition since he and his wife took over the newspaper 38 years ago.

Since then, circulation has quadrupled to 4,200. Mrs. Reeve says the couple goes out to dinner every night to get away from the ringing phones in their Victorian house, which doubles as the newspaper's offices.

Readers say the paper's popularity is due to the Reeves' sense for what news matters most to Sharon, population 15,042.

''Everybody wants to know everybody else's business and it's all in there,'' said Andy McAuliffe, owner of the downtown Convenience Food Mart, which sells 700 copies a week.

Engagements often head Page One, alongside notices for rubbish pickup and a column by the Sharon Historical Society that bemoans the town's growth from a somewhat remote rural community 30 miles south of Boston to a suburb.

''Many remember the social summers with people coming to the inns to spend the summer and providing work for the adolescents and women of the town,'' wrote historian Claire Forman in the May 8 edition.

But the newspaper's chief draw is the front-page police blotter reported by Bernice Leonard, who for 24 years has provided an account of the dark side.

''Had the DPW (Department of Public Works) remove a dead animal from a mailbox on Morse St. where someone had thoughtfully deposited it,'' read one recent blotter entry.

''Restored peace where there had been warring factions on Pond St.,'' read another.

To preserve the peace, Mrs. Leonard keeps all names out of the column. To preserve the virtue of young townspeople, the Reeves keep all liquor and cigarette ads out of the newspaper.

To preserve their integrity, they refuse to solicit ads, raise their rock- bottom advertising rates of $2.50 a column inch or expand the paper beyond 12 pages.

''One man cried practically when we told him he had to cut down on the size of his ads,'' said Mrs. Reeve.

The paper's size is set, however, by the Reeve's turn-of-the-century press, a loud and erratic machine that can handle only a dozen pages a week.

Founded in 1883, the Advocate was bought by Mrs. Reeve's father, E. Gilmore Richards, in 1919. The town's assessor and engineer, Richards bought the paper ''so he could print his own articles,'' Mrs. Reeve said.

While Richards wrote, his wife, Gertrude, managed the newspaper, making sure it came out every Thursday - a tradition her daughter has carried on.