PDFedit - Free (and open source) editor for manipulating PDF documents. GUI version + commandline interface.
PDF Joiner - This online tool allows you to join several PDF documents into a single file, free of charge.
Adobe Acrobat DC - Make your job easier with Adobe Acrobat DC, the trusted PDF creator. Use Acrobat to convert, edit and sign PDF files at your desk or on the go.
PDFChef Merge PDF - PDFChef Merge PDF is an online tool that allows you to merge multiple PDf files into one quickly and securely.
Master PDF Editor - Master PDF Editor is complete solution for editing PDF and XPS files.
PDFill - Open, View, Edit, Save and Print PDF Documents without Adobe Acrobat