Digital signature (eSignature) made easy with GroupDocs Signature. Create your electronic digital signature and digitally esign documents!...XLSX, XLSM, XLSB, OTS, XLTX, XLTM PowerPoint: PPT, PPTX, PPS,...\"xls\",\"xlsb\",\"xlsm\",\"xltm\",\"xltx\",\"csv\",\"bmp\",\"gif\"...