In this article I will explain with an example, how to automatically download PDF File using JavaScript.
The PDF file will be downloaded as BLOB using XmlHttpRequest AJAX call and then will be sent for download in the Browser using JavaScript.
Location of Files
The PDF file are stored in a folder named Files inside the project directory.
Automatically download PDF File using JavaScript
Note: You can also set URL of the PDF which can belong to either same server or any other server location.
Automatically download PDF File using JavaScript
Inside the window.onload event handler, the DownloadFile JavaScript function is called.
Inside the DownloadFile JavaScript function, the URL of the File is passed as parameter to the GET call of the JavaScript XmlHttpRequest call.
Then inside the onload event handler, the received Byte Array (Binary Data) is converted to BLOB object and the File is downloaded in Browser.
<html xmlns="">
    <script type="text/javascript">
        window.onload = function () {
            setTimeout(function () {
            }, 1000);
        function DownloadFile(fileName) {
            //Set the File URL.
            var url = "Files/" + fileName;
            //Create XMLHTTP Request.
            var req = new XMLHttpRequest();
  "GET", url, true);
            req.responseType = "blob";
            req.onload = function () {
                //Convert the Byte Data to BLOB object.
                var blob = new Blob([req.response], { type: "application/octetstream" });
                //Check the Browser type and download the File.
                var isIE = false || !!document.documentMode;
                if (isIE) {
                    window.navigator.msSaveBlob(blob, fileName);
                } else {
                    var url = window.URL || window.webkitURL;
                    link = url.createObjectURL(blob);
                    var a = document.createElement("a");
                    a.setAttribute("download", fileName);
                    a.setAttribute("href", link);
Automatically download PDF File using JavaScript
Browser Compatibility

The above code has been tested in the following browsers only in versions that support HTML5.

Internet Explorer  FireFox  Chrome  Safari  Opera 

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