NEW YORK -- The IRS uses it to distribute tax forms over the Internet. Research reports often circulate in the format, too. So popular is the PDF that software companies use it to "print" their manuals.

The Portable Document Format, from Adobe Systems Inc., has become a de facto standard for electronic documents.

It has gained currency because Web pages and documents created with disparate programs can appear differently on different browsers and computers. With PDF, documents appear on screen or print out as the author intended.

Yet relatively few people have created their own PDFs. While Adobe's free PDF reader comes installed on most computers, the company charges hundreds of dollars for software to make PDFs.

A number of cheaper or free alternatives are available, thanks to Adobe's publishing (in PDF format, of course) of the PDF's specifications.

I tested two -- 1-Step RoboPDF and Pdf995 -- against Adobe's top-of-the-line Acrobat Professional. I found, sadly, that you get what you pay for.

Pdf995 from Software995 (free with ads, $9.95 without) lets you convert any document from any Windows application using the "print" function. The document goes to a PDF virtual printer, instead of a real printer. Think of all the paper you can save "printing" e-commerce receipts or Web articles!

The PdfEdit995 add-on lets you reduce image quality to make files smaller and embed PDFs with Web links that you can open in a browser from Adobe's free reader. PdfEdit995 is also free, though removing ads costs $9.95.

Signature995 (another $9.95 to remove ads, or $19.95 for all three) allows you to encrypt documents and prevent people from modifying or printing them without a password.

The software suite could use better instructions, and attempts to convert Web pages sometimes generated PDF images of the software's pop-up ads instead. Again, you get what you pay for.

RoboPDF, from eHelp Corp., costs $79 -- pricey, but cheaper than Adobe's $449 Acrobat Professional and $299 Acrobat Standard. A free home version produces a RoboPDF stamp at the bottom of each PDF page.

Like Pdf995, you can create PDF files using a virtual printer. But you can also create PDFs directly from the RoboPDF application, use toolbar buttons within Microsoft Office programs, right-click on a file name or icon, or drag the icon over the RoboPDF icon.

But oddly, opening a PDF file from the application generates a PDF of the PDF -- you lose embedded links and waste minutes for larger files. And once, while attempting to convert a Web page, RoboPDF captured just one photo. Still, RoboPDF is a bit more versatile and easier to use than the Pdf995 suite.

If you're really willing to pay, Adobe's Acrobat Standard is all that anyone but graphics and publishing professionals will really need.

Besides what you get elsewhere, Acrobat lets you exchange comments with other collaborators working on the same document -- and even turn a Web site into a PDF with embedded links for offline browsing.

Built-in optical character recognition can also lift text from scanned documents.

PDFs are typically read-only, but Acrobat lets you create forms that recipients can fill out, print and mail back -- even if they only have the free reader. To save and send back electronically, though, requires the paid version of Acrobat, unless you're the IRS and have paid Adobe extra to turn on those features in the reader.

Acrobat was also the most efficient at producing PDF documents. One Excel file became a 1.8-megabyte PDF using Acrobat, compared with 2.5 MB for Pdf995 and 2.7 MB for RoboPDF.

But with versatility comes complexity. There are usually multiple ways to perform any given task, and figuring out how can be challenging -- even after reading the "help" screens.

And different methods produce different results. Using default settings, a Web site with three photographs produced a 165-kilobyte file using Adobe's PDF printer but a 1,641 KB file using a toolbar button.

The Macintosh version of Adobe's software has most of the Windows functionality. The Mac OS X operating system comes with a rudimentary PDF-creation program, but comparing it with Adobe's is like pitting Little Leaguers against the Boston Red Sox.

Adobe's software can do much more than the cheaper or free varieties. Then again, if you're a home user just creating PDFs occasionally, you might want those extra bucks to blow on, say, a lobster dinner for 12.

My advice is to start cheap, then upgrade to Adobe's software later if you find you're creating PDFs regularly.