PDFedit is a free library and a set of tools to edit and manipulate PDF documents.
With the PDFedit library you can read, change and extract information from any PDF file. It is based on xpdf library and is multiplatform. PDFedit Tools includes the PDF manipulating library, the GUI, a set of command line tools and a pdf editor to manipulate any PDF files.
PDFedit is multiplatform, but please note that there is a new GUI (based on QT 4) for Windows. PDFedit is released under terms of GNU GPL version 2.