// Distinction of case for visual and non-visual signature
        if (visualSignature == null) // non-visual signature
        {
            // Set rectangle for non-visual signature to 0 0 0 0
            signatureField.getWidget().setRectangle(new PDRectangle());  // rectangle array [ 0 0 0 0 ]
            // Clear AcroForm / Set DefaultRessource
            acroFormDict.setItem(COSName.DR, null);
            // Set empty Appearance-Dictionary
            PDAppearanceDictionary ap = new PDAppearanceDictionary();
            COSStream apsStream = getDocument().createCOSStream();
            apsStream.createUnfilteredStream();
            PDAppearanceStream aps = new PDAppearanceStream(apsStream);
            COSDictionary cosObject = (COSDictionary)aps.getCOSObject();
            cosObject.setItem(COSName.SUBTYPE, COSName.FORM);
            cosObject.setItem(COSName.BBOX, new PDRectangle());
            
            ap.setNormalAppearance(aps);
            ap.getDictionary().setDirect(true);
            signatureField.getWidget().setAppearance(ap);
        }
        else // visual signature
        {
            // Obtain visual signature object
            List<COSObject> cosObjects = visualSignature.getObjects();
    
            boolean annotNotFound = true;
            boolean sigFieldNotFound = true;
            for ( COSObject cosObject : cosObjects )
            {
                if (!annotNotFound && !sigFieldNotFound)
                {
                    break;
                }
                
                COSBase base = cosObject.getObject();
                if (base != null && base instanceof COSDictionary)
                {
                    COSBase ft = ((COSDictionary)base).getItem(COSName.FT);
                    COSBase type = ((COSDictionary)base).getItem(COSName.TYPE);
                    COSBase apDict = ((COSDictionary)base).getItem(COSName.AP);
            
                    // Search for signature annotation
                    if (annotNotFound && COSName.ANNOT.equals(type))
                    {
                        COSDictionary cosBaseDict = (COSDictionary)base;
              
                        // Read and set the Rectangle for visual signature
                        COSArray rectAry = (COSArray)cosBaseDict.getItem(COSName.RECT);
                        PDRectangle rect = new PDRectangle(rectAry);
                        signatureField.getWidget().setRectangle(rect);
                        annotNotFound = false;
                    }
            
                    // Search for Signature-Field