MergePDF is an easy and simple tool which could help you batch merge PDF files (any number you want) into one PDF file quickly. It is based PDFBinder project (code.google.com/p/pdfbinder/).

The user interface is pretty self-explanatory. You can add source PDF documents by using the "Add file..." button, or by dragging the files in from a file browser. Documents can be moved up, moved down or remoevd by pressing the respective buttons in the toolbar. Press the "Merge" button when your list of documents seems fine.

The license of this software is Free, you can free download and free use this pdf software.