Microsoft Office 2007 SP2 Adds a PDF Writer to Word, Excel, PowerPoint, etc.
With Office 2007 SP2, you can save documents to Adobe PDF format without requiring external plugins.
openoffice
OpenOffice 3 can read Office 2007 Documents
OpenOffice.org have just released the first public beta of OpenOffice 3, a Microsoft Office like suite of programs that works across all platforms.
OpenOffice 3 = Free PDF Editor + Acrobat Writer
With OpenOffice, you can import PDF files into Draw (PowerPoint), edit the contents of the PDF file and then export the changed file as a hybrid PDF meaning you can later re-edit the generated PDF files back in OpenOffice.