To crawl and index the content of PDF files an iFilter is needed. A no cost iFilter is provided by Adobe for use with SharePoint Server 2010. The download is available here.
A complete and simple description on how to configure indexing of PDF content in SharePoint Server 2010 could be found in the Microsoft Knowledge Base in this article. Before installing and configuring the iFilter, you should install SharePoint Server 2010 (or Search Server 2010) and create the Search Service Application.
But remember, when working with PDF files in SharePoint, these files are not allways opened, when the user clicks the file names. Instead the user is asked to save the file. To avoid this behavior, open the General Settings for the web application and set the Browser File Handling from “Strict” to “Permissive”.