Kdan PDF Reader - The All-in-One Document Expert Designed for the Increasingly-mobile Workplace.
PDF Joiner - This online tool allows you to join several PDF documents into a single file, free of charge.
iText - iText is an intuitive and refined text editor with word processing completely rewritten in Cocoa...
PDFChef Merge PDF - PDFChef Merge PDF is an online tool that allows you to merge multiple PDf files into one quickly and securely.
Apache PDFBox - The Apache PDFBox™ library is an open source Java tool for working with PDF documents.
PDFill - Open, View, Edit, Save and Print PDF Documents without Adobe Acrobat