Converting from HWPFDocument to XWPFDocument or vice versa - apache-poi

Question

I have a Word document, where I have to replace text and save this document in Oracle database, in PDF format. Have someone any idea how to resolve this?
String inputFilename = "/root/GeneratorUmow/web/WEB-INF/umowy/kkb/wniosekozaciag.docx";
try(InputStream is = new FileInputStream(inputFilename)) {
dbd = new DokumentyBlobDAO();
db.setNazwaPliku("Wniosek_o_zaciagniecie.pdf");
db.setTypDokuemntu(876990);
if(du.getTypKlienta() == S_ID_Lead_Partner_Typ_Klienta_KKB) {
POIFSFileSystem fs = null;
fs = new POIFSFileSystem(is);
HWPFDocument doc = new HWPFDocument(fs); //funkcja zamyka inputstream
Range range = doc.getRange();
range.replaceText("my&&nazwa&&firmy", "KAKAOWY SZATAN");
//konwersja na pdf
FileOutputStream fos = new FileOutputStream(pathToDirectory + File.separator + folderName+File.separator + "wniosekzaciagniecie.docx");
doc.write(fos);
String inputChangeFile = pathToDirectory+ File.separator +folderName+File.separator+"wniosekzaciagniecie.docx";
InputStream inputstream = new FileInputStream(inputFilename);
length = inputChangeFile.length();
System.out.println("dlugosc lancucha " + length);
XWPFDocument document = new XWPFDocument(inputstream);
System.out.println("message3");
PdfOptions options = PdfOptions.create();
PdfOptions options = PdfOptions.create().fontEncoding("windows-1250");
System.out.println("message4");
OutputStream out = new FileOutputStream(new File(pathToDirectory+ File.separator +folderName+File.separator+"kakaowyszal.pdf"));
PdfConverter.getInstance().convert(document, out, options);
System.out.println("message5");
}
}
catch( Exception ex){
System.out.println("err" + ex);
return -1;
}