PDF Encrypt allows you to encrypt (using standard 40-bit or 128-bit supported by Acrobat Reader 5.0 and up) existing PDFs, set permissions, add user and owner password.
Downloads: 64020 - Shareware - Download Now

Split any size/type, compress, add password, Automatic SFV CRC32, Self-Join capabilities and more ...
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Merge PDF files into a single document. Split PDF into multiple files following a custom pattern similar to Word printing. Combine encrypted PDF with just a few clicks. Mix two PDF files.
Downloads: 86950 - Freeware - Download Now

PDF Split/Merge is a stand-alone application that can be used to split, merge, and manage your PDF files.
Downloads: 78177 - Shareware - Download Now

PDF Split/Merge is a stand-alone application that can be used to split, merge, and manage your PDF files, it is offered as an easy to use GUI (Graphical User Interface) application, and a command line application.
Downloads: 74430 - Shareware - Download Now