/**
         * Gets the {@link PdfSignatureAppDictionary} from this dictionary. If it
         * does not exist, it adds a new {@link PdfSignatureAppDictionary} and
         * returns this instance.
         * 
         * @return {@link PdfSignatureAppDictionary}
         */

        private PdfSignatureAppDictionary GetPdfSignatureAppProperty() {
            PdfSignatureAppDictionary appPropDic = (PdfSignatureAppDictionary) GetAsDict(PdfName.APP);
            if (appPropDic == null) {
                appPropDic = new PdfSignatureAppDictionary();
                Put(PdfName.APP, appPropDic);
            }
            return appPropDic;
        }
        /**
         * Gets the {@link PdfSignatureAppDictionary} from this dictionary. If it
         * does not exist, it adds a new {@link PdfSignatureAppDictionary} and
         * returns this instance.
         *
         * @return {@link PdfSignatureAppDictionary}
         */

        private PdfSignatureAppDictionary GetPdfSignatureAppProperty()
        {
            PdfSignatureAppDictionary appPropDic = (PdfSignatureAppDictionary)GetAsDict(PdfName.APP);

            if (appPropDic == null)
            {
                appPropDic = new PdfSignatureAppDictionary();
                Put(PdfName.APP, appPropDic);
            }
            return(appPropDic);
        }