PDF files or Adobe Acrobat reader files can be major problems for search engine spiders. Although some search engines can index them, the pages must be interpreted into HTML and can lose much of their content.

This is not to say that they are not good to use. Actually, Adobe Acrobat is a really nice piece of software that I often use myself. What you need to do is use things like Adobe Acrobat on pages further in your web site. Never place PDF files on pages like your home page, or anywhere near any important pages that you want spiders to index.

If your site uses Adobe Acrobat, a good idea is to dedicate a page just for your Acrobat files. Offer a non-text link from your home page to get there as needed.