This Java program splits one PDF document into two PDF files using Qoppa’s library jPDFAssemble: a first PDF document (“split1”) which contains the first and second page and a second PDF document (“split2”) which contains the third and fourth page of the original PDF.

// Load the original PDF document
PDFAssemble pdfDoc1 = new PDFAssemble ("doc1.pdf", null);
 
// create 2 new PDF documents
PDFAssemble split1 = new PDFAssemble();
PDFAssemble split2 = new PDFAssemble();
 
// Add pages 1 and 2 to split1 
split1.appendPage (pdfDoc1, 0);
split1.appendPage (pdfDoc1, 1);
 
// Add pages 2 and 3 to split2
split2.appendPage (pdfDoc1, 2);
split2.appendPage (pdfDoc1, 3);
 
// save two new PDF documents
split1.saveDocument ("split1.pdf");
split2.saveDocument ("split2.pdf");

Download Full Java Sample:
https://www.qoppa.com/files/pdfassemble/guide/sourcesamples/SimpleSplit.java