diff --git a/examples/oo-empty.pdf b/examples/oo-empty.pdf
new file mode 100644
index 0000000..f5b4827
Binary files /dev/null and b/examples/oo-empty.pdf differ
diff --git a/examples/oo-empty_signed.pdf b/examples/oo-empty_signed.pdf
new file mode 100644
index 0000000..35c10eb
Binary files /dev/null and b/examples/oo-empty_signed.pdf differ
diff --git a/src/pdfsign.hxx b/src/pdfsign.hxx
index 6e3c64e..6d5686b 100644
--- a/src/pdfsign.hxx
+++ b/src/pdfsign.hxx
@@ -33,6 +33,7 @@ class PdfSign: public QMainWindow, protected Ui::Pdfsign {
       if (fileName.isEmpty()) return;
       _pdf = std::shared_ptr<Poppler::Document>(Poppler::Document::load(fileName));
       showPage();
+      
     }
   public:
     void showPage(int pageNumber=0) {
@@ -42,6 +43,47 @@ class PdfSign: public QMainWindow, protected Ui::Pdfsign {
       _pdfDisplay->setPixmap(QPixmap::fromImage(pdfPage->renderToImage()));
       return;
     }
+    void sign(QString filename) {
+      PdfSigIncMemDocument doc(filename.c_str());
+      char                    *buffer = NULL;
+      buffer = (char *)malloc(809600);
+      PdfOutputDevice         output(buffer, 809600);
+      PdfSignOutputDevice     signOutput(&output);
+      signOutput.SetSignatureSize(2048);
+      printf( "Page count:%d\n", doc.GetPageCount());
+      
+      PdfSigIncSignatureField *sign = doc.GetSignatureField();
+      sign->SetSignatureDate(PdfDate());
+      sign->SetSignatureReason(L"I dont agree");
+      //sign->SetSignatureImage("e:\\sign.jpg", 0, 100, 200, 100, 100);
+      sign->SetSignatureText(L"Hello World", 0, 100, 200, 100, 100, 12);
+      doc.Initialize();
+      doc.CreateVisualSign();
+      doc.Write(&signOutput);
+      printf( "Has Signature:%d\n", signOutput.HasSignaturePosition());
+      /*
+      char buff[809600] = {0};
+      size_t len;
+      BYTE *Signature = NULL;
+      DWORD cbSignature = 0;
+      
+      signOutput.AdjustByteRange();
+      signOutput.Seek(0);
+      len = signOutput.ReadForSignature(buff, 809600);
+      printf("total tbs size: %d\n", len);
+      SignMessage( (BYTE *)buff, len, &Signature, &cbSignature);//Digital signing using MSCAPI
+      printf("signature size: %d\n", cbSignature);
+      const PoDoFo::PdfData *sig = new PoDoFo::PdfData((char *)Signature, cbSignature);
+      signOutput.SetSignature(*sig);
+          */
+      signOutput.Flush();
+      
+      FILE *fp = NULL;
+      fp = fopen("/tmp/signed.pdf", "wb" );
+      fwrite( buffer, signOutput.GetLength(), 1, fp );
+      fclose(fp);
+      free(buffer);
+    }
   private:
     std::shared_ptr<Poppler::Document> _pdf;
 };