I recently found out that OpenOffice 3.0 has a PDF Import Extension that will allow a user to import a PDF and possibly edit it. It depends on how the original document was created but it may be of use if you need to edit a PDF document.
After downloading the Extension open OpenOffice, go to Tools, and select Extension Manager. Add the extension you downloaded earlier. Once you have installed the extension, you can open the pdf file using file open. Make sure you change the file type to PDF first. You can open the document in either Draw (The default) or Impress. Once you are done editing the document can be exported back out as a PDF.
PDF Import Extension:
http://extensions.openoffice.org/en/project/pdf-import-apache-openoffice (updated)
OpenOffice:
http://www.openoffice.org/
OpenOffice Portable (So you don't have to install anything)
http://download.cnet.com/OpenOffice-org-Portable/3000-2064_4-10526815.html