Windows: PDF Rider is a simple but effective tool for merging and splitting PDF files, extracting and inserting pages, and performing other PDF manipulations.
PDF Rider is a GUI wrapper for the popular pdftk PDF manipulation tool. Documents are loaded inside PDF Rider using the default PDF viewer on your machine — such as Adobe Reader — but editing is handled by the pdtfk library. You can merge and split documents, extract, insert, and rotate pages, and decrypt and encrypt documents. If you need to separate all the pages of a document into unique files the burst function is especially handy.
PDF Rider is freeware, Windows only, and requires Microsoft .NET 3.5 or above.