PDF Joiner - This online tool allows you to join several PDF documents into a single file, free of charge.
PDF Shaper - a collection of PDF tools and utilities to modify and optimize your PDF documents and its content
DocuPUB - DocuPUB is an online file converter, file merger, file compressor, and file resizing tool.
PDFsam - PDFsam Basic, a free, open source, multi-platform software designed to split, merge, extract pages, mix and rotate PDF files
PDFChef Merge PDF - PDFChef Merge PDF is an online tool that allows you to merge multiple PDf files into one quickly and securely.
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.