Silverlight, the rich media technology that Microsoft trotted out last week, isn't the company's only attack on Adobe Systems's multimedia dominance. In addition to Silverlight, touted as a potential Flash-killer, Microsoft is quietly putting the moves on Adobe's other popular consumer technology, the Portable Document Format (PDF).

For more than a decade, PDF has been the most popular way of saving and exchanging static, graphics-rich documents so they can be easily read on any computer. Just as important, PDFs can be sent to any printer without the need of extra drivers, or the fear of garbled text or improperly displayed graphics.

As with Flash, Adobe gives away software to view PDFs -- in this case, the Adobe Reader (formerly Acrobat Reader) -- to consumers in order to sell pricey software to create PDFs to graphic designers, publishers and other creative types. Adobe's entry-level Acrobat 8 Standard costs US$299 per user, with higher-end versions running more.

But for XML Paper Specification, or XPS -- Microsoft's new rival to PDF -- the Redmond company is making the software for free to both consumers and pros.

In mid-April, Microsoft released a combination XPS reader and creator for free download. The software runs on Windows XP and both the 32-bit and 64-bit versions of Windows Server 2003.

Moreover, XPS is built into Vista itself, meaning users can open up and print XPS documents in Internet Explorer 7.0 and create XPS documents from any relevant application by simply choosing the "print to XPS" command.

Color true, comments allowed

Microsoft did not comment for this story, though it is likely to make some XPS-related announcements at its Windows Hardware Engineering Conference (WinHEC) in mid-May.

Some independent supporters say XPS's price -- it's also being licensed for free to potential software and hardware partners -- can't be beat.

"XPS is built into Windows' APIs, and the tools to manipulate them are free," said RanDair Porter, president of Pagemark Technology, a company offering XPS support services. "If you want to do this with Adobe, you have to go and buy a bunch of software."

Microsoft also claims a number of technical advantages for XPS. For one, XPS' use of compressed XML makes XPS documents more searchable and easier to manipulate by outside applications.

XPS also supposedly renders on-screen colors and images to paper better than other technologies, including PDF. Finally, XPS serves as both a file format and a printer language similar to Printer Command Language, which was developed by Hewlett-Packard Co., and PostScript, which was developed by Adobe. That, says Microsoft, allows it accelerate print times.

"Users have been complaining for years, 'Why does it take so long to print? Why is the color on my screen different than what's on my printer?'" said Dave Jollota, chief operating officer at QualityLogic, a company that is helping vendors add XPS support to their products. "If you can use the same language to put dots on the screen and put dots on paper, bypassing the conversion process, I do believe the color and the throughput will be better." By contrast, PDF documents still need to be converted to PostScript before they are printed, according to Porter.

XPS also offers more sophisticated digital rights management features than PDF, according to Mike Hamilton, vice president of product management at MadCap Software, whose upcoming Blaze publishing software will support XPS documents and let users add comments to them.

"With PDF, I can read comments, but if I don't have Acrobat Professional, I can't add them," he said. "So we're pretty excited about XPS."