Another way to split a PDF is by using a free app called PDF Merger & Splitter ... the chosen pages in your PDF using both ...

Let me introduce you to iLovePDF which brings to you a set of free online PDF Tools that lets you merge, split, compress, unlock, watermark, rotate PDF files, and convert PDF to Word, PowerPoint ...

Alternate Mix: This plug-in is used to combine the pages of two PDF files so that each page appears in an alternate form. PDFSam is free PDF editing software easily available on the Internet.