PDF Joiner - This online tool allows you to join several PDF documents into a single file, free of charge.
PDFTK Builder - PDFTK Builder is a free graphical interface to for PDFTK, making it much easier to use.
PDFChef Merge PDF - PDFChef Merge PDF is an online tool that allows you to merge multiple PDf files into one quickly and securely.
QPDF - QPDF is a command-line program that does structural, content-preserving transformations on PDF...
DocuPUB - DocuPUB is an online file converter, file merger, file compressor, and file resizing tool.
iSafePDF - iSafePDF is a free open source PDF protection software.