Many major search engines now have the capability to index PDF files and return them in search results.  If you are a Web site owner with PDF files on your site, this is good news.  If you are an SEO, you also know that the new capability presents potential usability problems.  And what exactly is the big deal? Let's find out.

Searching for "blessing of a Christmas tree" on Google returns a link to a PDF file as the first result:  http://www.google.com/search?sourceid=navclient&ie=UTF-8&oe=UTF-8&q=BLESSING+OF+A+CHRISTMAS+TREE

If searchers click on it, the link automatically opens a PDF file with no navigation back to the main site.  Users are trapped! So, what's going on and, more importantly, how to do we fix it?  Essentially, the PDF format is not the culprit; the real problem is the author's failure to create the files with Web users in mind.

PDF authoring software, such as Adobe Acrobat, offers the ability to include both a navigational structure and hyperlinks on a PDF page.  Ideally, the best solution is to create your pages in HTML, rather than PDF format.  Depending on the purpose, however, a PDF format can be preferable.  For example, PDF files offer better functionality for pages that are commonly printed, such as order forms and price lists.
 
To avoid the PDF USER TRAP, you will have to republish your files, adding some type of navigation structure and/or link back your main Web site.  This is the best option for SEO's, because it allows the pages to still be indexed.  If this is not an option, the next best solution is to place all of your PDF files in a single folder and do a robots exclusion.