The PR plan is set to run alongside a £3m ad campaign.
Launch PR managing director Johnny Pitt said: 'In the past, Cadburys has under-invested in the brand, which has huge appeal across all age-groups. We are totally repositioning it for a 25-35 female-focused audience.'
Pitt said the aim was to make Buttons one of Cadbury's biggest brands, and that the campaign would be themed around the simplicity of the milk-chocolate product.
The PR activity will involve editorial and targeted promotions, probably including a text messaging campaign.
'We will be negotiating media partnerships based around this idea of making your life simple. The partnerships will be with slightly unexpected media such as The Financial Times, and the Daily Mail property section,' said Pitt.
The activity will also see the traditional 'Cadburyland' cartoon packaging replaced with a more contemporary look.
The project brief work was won following a competitive pitch with Cadbury's retained agency PR21, which continues to handle day-to-day PR for many Cadbury brands.
Launch PR will report to brand manager Nina Leijerstam.