PDF Joiner - This online tool allows you to join several PDF documents into a single file, free of charge.
PDFtk - PDFtk is a simple tool for doing everyday things with PDF documents.
PDFTK Builder - PDFTK Builder is a free graphical interface to for PDFTK, making it much easier to use.
Pdfinfo - Pdfinfo is a PDF document information and metadata extractor tool.
PDFChef Merge PDF - PDFChef Merge PDF is an online tool that allows you to merge multiple PDf files into one quickly and securely.
Edit PDF metadata - Edit PDF metadata is an online tool from PDFCandy that can manipulate PDF info and metadata.