After nearly 15 years in use, PDF is as popular as file formats get. That is, of course, unless you include .doc, .xls and .ppt, Microsoft's pervasive, nay, inescapable Office formats. What the recent Microsoft/Adobe tussle over PDF-output capabilities failed to really expose is that Microsoft lacks a single format that can effectively pull together multiple files into a single, compound document.

Although many think of PDF as the go-to format for online document downloads and printing, what drives a lot of business users to PDF is the need to combine disparate files into a single document. Opening an Excel file in Word or a Word file in PowerPoint is a process fraught with compromises, and you can forget about going the other way. Yet documents from any application that can print can be turned into a PDF, and that includes everything in the Office suite as well as Internet Explorer, Access and Publisher. And that doesn't even scratch the surface of the close working relationship between PDF and various image file formats.

To revisit a little history, Adobe introduced PDF in 1993, and it put it on the map by giving away the ubiquitous Reader for free. By letting more than 1,200 independent software vendors make use of the format, Adobe has steadily nurtured PDF from cult favorite (by the mid 1990s) to de facto standard (by the late 1990s) to today's ISO-certified standard for archiving (PDF/A) and printing (PDF/X). To date, more than 500 million Adobe Readers have been downloaded and more than 200 million PDF documents are available for download on the Web. The format is the foundation of Adobe's "Intelligent Documents" product segment, which this year will account for more than one third ($700 million) of the company's nearly $2 billion in revenue.

Bowing to the popularity of PDF, Microsoft had planned to include the format as an output option in the next release of the Office suite. But in early June, the company backed away from that plan, citing pressure from Adobe. What remains to be seen is whether Microsoft will make the PDF option available as a free download or whether it will bow to Adobe's wishes and charge for that feature as an add-on option.

To be sure, giving millions of users the ability to turn Office documents into PDFs will knock a lot of wind out of the sails/sales of Adobe and plenty of other vendors. But it still won't give Microsoft a universal format and universal content creation tool of its own. To get there, Microsoft's fledgling XPS (XML Paper Specification), codenamed Metro, will have to beat the odds and supplant PDF as the most portable of document formats.

If PDF is such an "open standard," why not let Microsoft give PDF creation capabilities away for free? In a prepared statement, Adobe says its concern is that "Microsoft will fragment and possibly degrade existing and established standards, including PDF, while using its monopoly power to introduce Microsoft-controlled alternatives -- such as XPS. The long-term impact of this kind of behavior is that consumers are ultimately left with fewer choices."

For now, users who need to create, secure and publish compound documents will continue to turn to Acrobat Standard and Professional and the scores of competitive products that let you open disparate file types and output to PDF. In the imaging arena, leading lights include Nuance PaperPort and OmniForm, Abbyy FineReader and eCopy's just-released upgrade of eCopy Desktop.