PDFsam is an open source app that allows you to split, merge, extract pages, rotate and mix PDF files.You can merge PDF files by selecting the pages, combining bookmarks and interactive forms. Alternate Mix allows you to join any two PDF files together.Rotate lets you rotate (obviously) all or parts of a PDF file.Split lets you split a PDF file at given page numbers, bookmarks or size.Extract allows you to extract pages from any PDF file.