I recently came across a quote from a web marketer saying that people who "include PDF documents [in their websites] don't realize the search engines cannot see this text." Fortunately, that's not really the case. I believe the real problem is that most people don't take the appropriate care when creating their PDFs. In fact, PDF documents can be a great way to improve your search traffic, as long as you follow a few simple rules.

First, make sure your PDFs actually contain text. The search engines will crawl the text of a PDF just as they crawl a web page. Most graphics programs are capable of adding text to the graphics they create - but this is not actually "machine text". If your PDF document was originally created in a graphics program, there's a good chance that the search engines can't read it. Stick with Word or other word processing programs for creating your original documents.

Make sure your text is optimized, just like a webpage. It needs to contain headlines and your important keywords. I haven't figured out what the keyword density in a PDF should be yet, but I would suggest aiming for 3-6%.

Remember the crawl factor. Include links to your PDF documents from your webpages and vice versa, and use the appropriate anchor text. Depending on which version of Acrobat you're using, there's a good chance that the links from your Word document will NOT automatically convert into links in your PDF document. Don't forget to use the Link tool in Acrobat to recreate your hyperlinks.

If you're including graphics in your PDF, optimize the graphics before inserting them into the original document. This will help keep your PDF file size down - files that are too large can be abandoned by the search engines before the crawl is done.

Don't forget to update the document properties. Often, the name you give your original document will be automatically inserted as the title in the PDF file's properties. The PDF document properties - especially the title tag - are similar to an html document's meta data. Something like "Report1.doc" isn't going to help your search traffic much. After the PDF has been created, be sure to open it in Acrobat and tweak all of the properties and add the appropriate keywords.

Don't be an early adopter. There's no need to upgrade to the latest and greatest version of Acrobat since the search engines' capabilities often lag behind the software's development. Just because Acrobat 8 can create 3D CAD drawings, doesn't mean Google can read them. If you do have the newest version of Acrobat, save your document for a lesser version (5 or 6).

Optimize the final PDF file. Be sure to use the built in PDF optimizer and Optimize For The Web options. This will help keep your file size as small as possible and also allow for an interlaced display.

Time to implement: With PDF documents, it's creating the original file that is the time consuming part. After all that work, it's definitely work the extra 10 minutes or so to make the few necessary tweaks in Acrobat.