Merge PDFs into one using Java & PDFBox API

 //Suppose we want to merge one pdf with another main pdf

              InputStream is1 = null;

              if (file1 != null) {

                     FileInputStream fis1 = new FileInputStream(file1);

                     byte[] file1Data = new byte[(int) file1.length()];

                     fis1.read(file1Data);

                     is1 = new java.io.ByteArrayInputStream(file1Data);

              }

              //

              InputStream mainContent = <ur main content>

              org.apache.pdfbox.pdmodel.PDDocument mergedPDF = new org.apache.pdfbox.pdmodel.PDDocument();

              org.apache.pdfbox.pdmodel.PDDocument mainDoc = org.apache.pdfbox.pdmodel.PDDocument.load(mainContent);

              org.apache.pdfbox.multipdf.PDFMergerUtility merger = new org.apache.pdfbox.multipdf.PDFMergerUtility();

              merger.appendDocument(mergedPDF, mainDoc);

              PDDocument doc1 = null;

              if (is1 != null) {

                     doc1 = PDDocument.load(is1);

                     merger.appendDocument(mergedPDF, doc1);

                    //1st file appended to main pdf");

              }

             

              ByteArrayOutputStream baos = new ByteArrayOutputStream();

              mergedPDF.save(baos);

//Now either u save it here or convert into InputStream if u want

              ByteArrayInputStream mergedInputStream = new ByteArrayInputStream(baos.toByteArray());