The first thing you should probably do is to make it so that, in your document libraries, PDF files should show up with the correct Icon in the ‘type’ column. To do that, follow the directions here:
http://allthingsdotnet.net/?p=793

Then, there are a few more steps necessary to enable SharePoint 2010 to actually search PDF documents.

First, download the Adobe iFilter application here:
http://www.adobe.com/support/downloads/detail.jsp?ftpID=2611&PID=4172469

Next, run this application on your indexing server for SharePoint. If you don’t have a separate indexing server, run it on your SharePoint installation.

Lastly, you’ll need to enable the pdf extension in your searches. Go to Central Administration/Search Service Application Search Administration.
There, on the left nav, click on the ‘File Types’ link. Once there, click on the ‘New File Type’ link and add ‘pdf’ to the list. Once you recrawl, that should be all you need to do.