The PDF Import Extension for OpenOffice.org lets you modifying a PDF files for which there is no original source file. PDF documents are imported in Draw and Impress which preserves the layout and allows basic editing. Useful for changing dates, numbers or small portions of text. Native PDF forms are not supported.
This is just a beta version of the extension and requires the OpenOffice.org 3.0 beta. Please consult the developers homepage for contact details, they welcome any feedback you have.