PDFTK Builder - PDFTK Builder is a free graphical interface to for PDFTK, making it much easier to use.
PDF Arranger - Small python-gtk application, which helps the user to merge or split pdf documents and rotate, crop...
QPDF - QPDF is a command-line program that does structural, content-preserving transformations on PDF...
Debenu PDF Tools - Simple to use solution to merge PDF files, edit document properties, add and edit custom metadata, convert images to PDF, convert PDF to text and much more.
iSafePDF - iSafePDF is a free open source PDF protection software.
PDF Joiner - This online tool allows you to join several PDF documents into a single file, free of charge.