Add a digital signature with Gnostic PDFone

See more:

PDF

C#5.0

PDFDocument doc = new PDFDocument("your-license-key");
            frmDigital f = new frmDigital();

           f.txtPDFLoad.Text = theDialog.FileName;
           string path = theDialog.FileName.ToString();
           f.txtPDFLoad.Text = path;
            // Load an existing PDF
            doc.Load(theDialog.FileName);

             
            doc.AddSignature(
                  @"C:\Users\nikola.nedelkovski\Downloads\VodovodTestSertifikat\VodovodTestSertifikat.pfx",       // signature file
                  "",                           // signature password
                  "Approved",                           // reason
                  "Duna",                        // location
                  "Signed",                   // contact info
                  1,                                    // page number
                  "fldSign",                            // signature field name
                  new RectangleF(4f, 4.8f, 2f, 0.4f));  // location

            // Write signed document to file
            doc.Save("signed_doc.pdf");

           
            doc.Close();

Here is code how i add digital signature but code fail on password file. I have not stetted password on my pfx file and when i try to add signature it fails. Any idea how to make method without password comparation?