I solve it like that but it is just run for word document any suggestion how can i use it to merge with pdf excel and picture ?

 public void mergeDocx(InputStream s1, InputStream s2, OutputStream os) throws Exception {
        WordprocessingMLPackage target = WordprocessingMLPackage.load(s1);
        insertDocx(target.getMainDocumentPart(), IOUtils.toByteArray(s2));
        SaveToZipFile saver = new SaveToZipFile(target);
        saver.save(os);
    }
    private static void insertDocx(MainDocumentPart main, byte[] bytes) throws Exception {
        AlternativeFormatInputPart afiPart = new AlternativeFormatInputPart(new PartName("/part" + (chunk) + ".docx"));
        afiPart.setContentType(new ContentType(CONTENT_TYPE));
        afiPart.setBinaryData(bytes);
        Relationship altChunkRel = main.addTargetPart(afiPart);
        CTAltChunk chunk = Context.getWmlObjectFactory().createCTAltChunk();
        chunk.setId(altChunkRel.getId());
        main.getContent().add(1,chunk); 
// i add this method 
    ```