Free PdfMerge is a tool that uses the PDFSharp library and is both command line or General user interface driven. It can easily split and or merge pdf documents very easily with limited steps. There are more complex options for the more advanced user if needed which will allow you to split documents with several different configuration options. PdfMerge is very efficient and simple to use. There are additional options: Extract - Rotate - Mix - Compose - Re-Order.