The intellectual property provider, which specialises in patent translations, said it plans to raise gross proceeds of £40mln through the placement of 12.1mln ordinary shares at 330p each.
The proceeds of the placement will be used to part-fund its $82.5mln full takeover of San Francisco-based group LUZ, which supplies translation and localisation services for life science companies.
The rest of the consideration will be funded using existing cash resources and a new $26.3mln loan with Barclays Bank.
"Our Life Sciences activities will represent over 30% of the enlarged group's revenues, with strong margins and further opportunities for growth,” RWS chairman Andrew Brode said.
“The Life Sciences sector also provides the potential for the enlarged group to develop and expand its other services, especially in patent translation and foreign filing.”
At the annual results in December, RWS suggested that further acquisitions could be on the horizon after reporting record revenues and profits.
Adjusted pre-tax profit jumped 35% to £30.6mln in the year ended 30 September 2016 as sales rose 28% to £122mln, thanks in part by 11 months of contribution from recently acquired Corporate Translations Inc.
"The group's strong cash generation and healthy balance sheet leave us well positioned to pursue that growth through acquisitions and organic investment, whilst also maintaining our progressive dividend policy," Brode said at the time.
In January the group said it has appointed its chief financial officer Richard Thompson as its new chief executive. Thompson will step into the role on 1 April while the search for a new CFO is underway.
Shares in RWS rose 4.22% to 352.53p in afternoon trade.