diff --git a/README.md b/README.md
index 56e928a..45a83b2 100644
--- a/README.md
+++ b/README.md
@@ -1,5 +1,6 @@
 # ZgaPdfSigner
 A javascript tool to sign a pdf in web browser.  
+And it also can be used in Google Apps Script.  
 
 PS: __ZGA__ is the abbreviation of my father's name.  
 And I use this name to hope the merits from this application will be dedicated to my parents.
@@ -15,7 +16,7 @@ Just import the dependencies and this tool.
 ```html
 <script src="https://unpkg.com/pdf-lib/dist/pdf-lib.min.js" type="text/javascript"></script>
 <script src="https://unpkg.com/node-forge/dist/forge.min.js" type="text/javascript"></script>
-<script src="https://github.com/zboris12/zgapdfsigner/releases/download/1.0.0/zgapdfsigner.js" type="text/javascript"></script>
+<script src="https://github.com/zboris12/zgapdfsigner/releases/download/1.1.0/zgapdfsigner.js" type="text/javascript"></script>
 ```
 
 ## Let's sign
@@ -35,7 +36,7 @@ async function sign1(pdf, cert, pwd){
     p12cert: cert,
     pwd: pwd,
   };
-  var signer = new PdfSigner(sopt);
+  var signer = new Zga.PdfSigner(sopt);
   return await signer.sign(pdf);
 }
 ```
@@ -67,7 +68,7 @@ async function sign2(pdf, cert, pwd, imgdat, imgtyp){
       imgType: imgtyp,
     },
   };
-  var signer = new PdfSigner(sopt);
+  var signer = new Zga.PdfSigner(sopt);
   return await signer.sign(pdf);
 }
 ```
@@ -78,9 +79,41 @@ Sign with a visible signature of drawing a text.
 //TODO
 ```
 
+Use it in Google Apps Script
+
+```js
+// Simulate setTimeout function for pdf-lib
+function setTimeout(func, sleep){
+  Utilities.sleep(sleep);
+  func();
+}
+// Simulate window for node-forge
+var window = globalThis;
+// Load pdf-lib
+eval(UrlFetchApp.fetch("https://unpkg.com/pdf-lib@1.17.1/dist/pdf-lib.min.js").getContentText());
+// Load node-forge
+eval(UrlFetchApp.fetch("https://unpkg.com/node-forge@1.3.1/dist/forge.min.js").getContentText());
+// Load ZgaPdfSigner
+eval(UrlFetchApp.fetch("https://github.com/zboris12/zgapdfsigner/releases/download/1.1.0/zgapdfsigner.js").getContentText());
+
+// Load pdf, certificate
+var pdfBlob = DriveApp.getFilesByName("_test.pdf").next().getBlob();
+var certBlob = DriveApp.getFilesByName("_test.pfx").next().getBlob();
+// Sign the pdf
+var sopt = {
+  p12cert: new Uint8Array(certBlob.getBytes()),
+  pwd: "some passphrase",
+};
+var signer = new Zga.PdfSigner(sopt);
+var u8arr = await signer.sign(new Uint8Array(pdfBlob.getBytes()));
+// Save the result pdf to some folder
+var fld = DriveApp.getFolderById("a folder's id");
+fld.createFile(Utilities.newBlob(u8arr, "application/pdf").setName("signed_test.pdf"));
+```
+
 ## Detail of SignOption
 
-* __p12cert__:  string :point_right: A raw data of the certificate 
+* __p12cert__:  (Uint8Array|ArrayBuffer|string) :point_right: Certificate's data
 * __pwd__:      string :point_right: The passphrase of the certificate
 * __reason__:   string :point_right: (Optional) The reason for signing
 * __location__: string :point_right: (Optional) Your location
diff --git a/closure/zb-externs.js b/closure/zb-externs.js
new file mode 100644
index 0000000..ab09bbb
--- /dev/null
+++ b/closure/zb-externs.js
@@ -0,0 +1,39 @@
+/**
+ * the base point of x, y is top left corner.
+ * @typedef
+ * {{
+ *    x: number,
+ *    y: number,
+ *    w: number,
+ *    h: number,
+ * }}
+ */
+var SignAreaInfo;
+/**
+ * @typedef
+ * {{
+ *    area: SignAreaInfo,
+ *    pageidx: (number|undefined),
+ *    imgData: (Uint8Array|ArrayBuffer|string|undefined),
+ *    imgType: (string|undefined),
+ *    text: (string|undefined),
+ *    fontData: (PDFLib.StandardFonts|Uint8Array|ArrayBuffer|string|undefined),
+ *    img: (PDFLib.PDFImage|undefined),
+ *    font: (PDFLib.PDFFont|undefined),
+ * }}
+ */
+var SignDrawInfo;
+/**
+ * @typedef
+ * {{
+ *    p12cert: (Uint8Array|ArrayBuffer|string),
+ *    pwd: string,
+ *    reason: (string|undefined),
+ *    location: (string|undefined),
+ *    contact: (string|undefined),
+ *    signdate: (Date|undefined),
+ *    signame: (string|undefined),
+ *    drawinf: (SignDrawInfo|undefined),
+ * }}
+ */
+var SignOption;
diff --git a/test.html b/test.html
index aaecd2b..72d2977 100644
--- a/test.html
+++ b/test.html
@@ -39,9 +39,8 @@ function testSign(imgdat, imgtyp){
 	var kf = document.getElementById("kkk").files[0];
 	readAsArrayBuffer(fil, function(a_pdf){
 		readAsArrayBuffer(kf, async function(b_kfbuf){
-			var b_kfdat = String.fromCharCode.apply(null, new Uint8Array(b_kfbuf));
 			var b_opt = {
-				p12cert: b_kfdat,
+				p12cert: b_kfbuf,
 				pwd: document.getElementById("pwd").value,
 			};
 			if(imgdat){
@@ -56,10 +55,10 @@ function testSign(imgdat, imgtyp){
 					imgType: imgtyp,
 				};
 			}
-			var b_signer = new PdfSigner(b_opt);
-			var b_blob = await b_signer.sign(a_pdf);
+			var b_signer = new Zga.PdfSigner(b_opt);
+			var b_u8s = await b_signer.sign(a_pdf);
 			document.getElementById("download").download = "zzzs3.pdf";
-			document.getElementById("download").href = window.URL.createObjectURL(b_blob);
+			document.getElementById("download").href = window.URL.createObjectURL(new Blob([b_u8s], {"type" : "application/pdf"}));
 			document.getElementById("download").click();
 		});
 	});
diff --git a/zgapdfsigner.js b/zgapdfsigner.js
index 50c6272..eea2057 100644
--- a/zgapdfsigner.js
+++ b/zgapdfsigner.js
@@ -1,44 +1,8 @@
-/**
- * the base point of x, y is top left corner.
- * @typedef
- * {{
- *    x: number,
- *    y: number,
- *    w: number,
- *    h: number,
- * }}
- */
-var SignAreaInfo;
-/**
- * @typedef
- * {{
- *    area: SignAreaInfo,
- *    pageidx: (number|undefined),
- *    imgData: (Uint8Array|ArrayBuffer|string|undefined),
- *    imgType: (string|undefined),
- *    text: (string|undefined),
- *    fontData: (PDFLib.StandardFonts|Uint8Array|ArrayBuffer|string|undefined),
- *    img: (PDFLib.PDFImage|undefined),
- *    font: (PDFLib.PDFFont|undefined),
- * }}
- */
-var SignDrawInfo;
-/**
- * @typedef
- * {{
- *    p12cert: string,
- *    pwd: string,
- *    reason: (string|undefined),
- *    location: (string|undefined),
- *    contact: (string|undefined),
- *    signdate: (Date|undefined),
- *    signame: (string|undefined),
- *    drawinf: (SignDrawInfo|undefined),
- * }}
- */
-var SignOption;
+'use strict';
 
-class PdfSigner {
+globalThis.Zga = {
+
+PdfSigner: class {
 	/**
 	 * @constructor
 	 * @param {SignOption} signopt
@@ -51,7 +15,7 @@ class PdfSigner {
 	/**
 	 * @public
 	 * @param {PDFLib.PDFDocument|Uint8Array|ArrayBuffer|string} pdf
-	 * @return {Blob}
+	 * @return {Promise<Uint8Array>}
 	 */
 	async sign(pdf){
 		/** @type {PDFLib.PDFDocument} */
@@ -74,8 +38,7 @@ class PdfSigner {
 
 		this.addSignHolder(pdfdoc);
 		var uarr = await pdfdoc.save({"useObjectStreams": false});
-		// return new Blob([uarr], {"type" : "application/pdf"});
-		var pdfstr = String.fromCharCode.apply(null, uarr);
+		var pdfstr = Zga.u8arrToRaw(uarr);
 
 		return this.signPdf(pdfstr);
 	}
@@ -91,7 +54,7 @@ class PdfSigner {
 		const SIGNATURE_LENGTH = 3322;
 
 		/** @const {VisualSignature} */
-		const visign = new VisualSignature(this.opt.drawinf);
+		const visign = new Zga.VisualSignature(this.opt.drawinf);
 		/** @const {PDFLib.PDFRef} */
 		const strmRef = visign.createStream(pdfdoc, this.opt.signame);
 		/** @const {PDFLib.PDFPage} */
@@ -118,7 +81,7 @@ class PdfSigner {
 			"M": PDFLib.PDFString.fromDate(this.opt.signdate),
 			"Prop_Build": pdfdoc.context.obj({
 				"App": pdfdoc.context.obj({
-					"Name": "ZbPdfSinger",
+					"Name": "ZgaPdfSinger",
 				}),
 			}),
 		};
@@ -167,7 +130,7 @@ class PdfSigner {
 	/**
 	 * @private
 	 * @param {string} pdfstr
-	 * @return {Blob}
+	 * @return {Uint8Array}
 	 */
 	signPdf(pdfstr){
 		if(!this.opt.signdate){
@@ -200,6 +163,9 @@ class PdfSigner {
 		// Remove the placeholder signature
 		pdfstr = pdfstr.slice(0, byteRange[1]) + pdfstr.slice(byteRange[2], byteRange[2] + byteRange[3]);
 
+		if(typeof this.opt.p12cert !== "string"){
+			this.opt.p12cert = Zga.u8arrToRaw(new Uint8Array(this.opt.p12cert));
+		}
 		// Convert Buffer P12 to a forge implementation.
 		var p12Asn1 = forge.asn1.fromDer(this.opt.p12cert);
 		var p12 = forge.pkcs12.pkcs12FromAsn1(p12Asn1, true, this.opt.pwd);
@@ -271,29 +237,11 @@ class PdfSigner {
 		// Place it in the document.
 		pdfstr = pdfstr.slice(0, byteRange[1]) + "<" + sighex + ">" + pdfstr.slice(byteRange[1]);
 
-		return this.rawToBlob(pdfstr, "application/pdf");
+		return Zga.rawToU8arr(pdfstr);
 	}
+},
 
-	/**
-	 * @private
-	 * @param {string} raw
-	 * @param {string=} typ
-	 * @return {Blob}
-	 */
-	rawToBlob(raw, typ){
-		var arr = new Uint8Array(raw.length);
-		for(var i=0; i<raw.length; i++){
-			arr[i] = raw.charCodeAt(i);
-		}
-		var opt = null;
-		if(typ){
-			opt = {"type" : typ};
-		}
-		return new Blob([arr], opt);
-	}
-}
-
-class VisualSignature {
+VisualSignature: class {
 	/**
 	 * @constructor
 	 * @param {SignDrawInfo=} drawinf
@@ -504,4 +452,31 @@ class VisualSignature {
 		}
 		return ret;
 	}
-}
\ No newline at end of file
+},
+
+/**
+ * @param {Uint8Array} uarr
+ * @return {string}
+ */
+u8arrToRaw: function(uarr){
+	/** @type {Array<string>} */
+	var arr = [];
+	for(var i=0; i<uarr.length; i++){
+		arr.push(String.fromCharCode(uarr[i]));
+	}
+	return arr.join("");
+},
+
+/**
+ * @param {string} raw
+ * @return {Uint8Array}
+ */
+rawToU8arr: function(raw){
+	var arr = new Uint8Array(raw.length);
+	for(var i=0; i<raw.length; i++){
+		arr[i] = raw.charCodeAt(i);
+	}
+	return arr;
+},
+
+};