PDFTK Builder - PDFTK Builder is a free graphical interface to for PDFTK, making it much easier to use.
PDFtk - PDFtk is a simple tool for doing everyday things with PDF documents.
QPDF - QPDF is a command-line program that does structural, content-preserving transformations on PDF...
AutoMetadata - AutoMetadata is a tool for exploring and manipulating metadata, document properties, and viewer preferences in multiple PDF documents.
iSafePDF - iSafePDF is a free open source PDF protection software.
Edit PDF metadata - Edit PDF metadata is an online tool from PDFCandy that can manipulate PDF info and metadata.