The first method is the cheapest, and uses a tool that is part of OS X: Automator. You can use Automator to create a workflow that can extract text from PDFs and save it as a text or RTF document.
Open Automator, which is in your Applications folder. On the first screen that displays, choose to make a Workflow. Click on Files & Folders in the leftmost column, then drag Ask For Finder Items from the second column to the larger section at the right of the Automator window.
Next, click on PDFs in the leftmost column, and drag Extract PDF Text from the second column to a point the first item you dragged to the right.
(Image Caption: A simple (and inexpensive) way to extract text from a PDF is to use an Automator workflow. After you've added the two Automator actions, your window should look like this.)