Adobe Systems has entered into a definitive agreement to acquire Omniture, a web analytics and online marketing company, in a transaction valued at approximately $1.8 billion.

According to Adobe, by combining its content creation tools and clients with Omniture’s web analytics, measurement and optimisation technologies, it will expand its addressable market and growth potential, and broaden its offerings to internet advertising, e-commerce and digital media markets.

The companies claimed that for designers, developers and online marketers, an integrated workflow with optimisation capabilities embedded in the creation tools, will streamline the creation and delivery of relevant content and applications. The acquisition of Omniture will further diversify Adobe’s business, adding a scalable SaaS platform.

Omniture said that joining Adobe will provide it global operational scale and the ability to more quickly penetrate new geographies and markets, thereby accelerating its go-to-market strategy and growth potential.

As part of the expected integration of the two companies, Omniture will become a new business unit within Adobe. Omniture’s CEO, Josh James, will join Adobe as senior vice president of the new business unit, reporting to Adobe’s president and CEO, Shantanu Narayen.

Shantanu Narayen, president and chief executive officer of Adobe, said: Adobe customers are looking to us for solutions to deliver engaging experiences and more effectively monetise their content and applications online. This is a game changer for both Adobe and our customers. We will enable advertisers, media companies and e-tailers to realise the full value of their digital assets.

Josh James, CEO of Omniture, said: Omniture’s mission has been to enable our customers to optimise every digital interaction. By joining forces with Adobe, we will accelerate our ability to deliver on that vision and together bring new innovation to the market that improves content engagement, advertising effectiveness and the overall user experience, which will drive more advertising dollars online.

Under the terms of the agreement, Adobe will make a tender offer to acquire all of the outstanding common stock of Omniture for $21.50 per share, a premium of 45% over its average closing price for the last 30 trading days.

The completion of the transaction, which is subject to customary government approvals and the satisfaction of other customary conditions, is expected to close in the fourth quarter of Adobe’s 2009 fiscal year.