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.
DocuPUB - DocuPUB is an online file converter, file merger, file compressor, and file resizing tool.
AutoMetadata - AutoMetadata is a tool for exploring and manipulating metadata, document properties, and viewer preferences in multiple PDF documents.
jPdf Tweak - jPDF Tweak is a Swiss Army Knife GUI application for PDF documents: combine, split, rotate, reorder...
Pdfinfo - Pdfinfo is a PDF document information and metadata extractor tool.