The software company said it is buying Web analytics firm Omniture for about $1.8 billion in an effort to make itself more competitive in the world of online commerce.

The maker Photoshop and Acrobat products said it will offer Omniture $21.50 per share in cash. That’s a 24% premium to Omniture’s Tuesday closing price of $17.32 per share. The deal is expected to close in the fourth quarter of Adobe’s fiscal year.

Omniture (OMTR), which is based in Orem, Utah, helps clients, including CNNMoney.com, understand how visitors traffic their Web sites and assists online businesses to target advertisements.

Adobe, which is based in San Jose, Calif. said the deal will help it “transform” e-commerce by combining its content creation tools with Omniture’s online measurement and optimization technologies to help “increase the value Adobe delivers to customers.”

“This is a game changer for Adobe and its customers,” said Shantanu Narayen, chief executive of Adobe, in a statement. “We will enable advertisers, media companies and e-tailers to realize the full value of their digital assets.”