Hello!
Very easy
Each page in report is separated report
for example
i create 3 report with static text
then i fill this report with data and receive 3 files with extention
*.jrprint
In end i gather this files in one pdf file

for filling report with data

String sourceFileName = "file.jasper";
String printFile="file.jrprint";
JasperFillManager.fillReportToFile(sourceFileName,printFile,params,
dataSources);

for gathering files in one report

for (Iterator iter = reportFiles.iterator(); iter.hasNext();) {
            String fileName = (String) iter.next();
            try {
                printList.add(JRLoader.loadObject("file.jrprint"));
            } catch (JRException e1) {
                e1.printStackTrace();
            }
        }
        JRPdfExporter exporter=new JRPdfExporter();
        exporter.setParameter(JRExporterParameter.JASPER_PRINT_LIST,
printList);
        exporter.setParameter(JRExporterParameter.OUTPUT_FILE_NAME,
destFileName);
        try {
            exporter.exportReport();
        } catch (JRException e) {
            e.printStackTrace();
        }