Unable to download file from webapp using android studio

Question

I created an web app using android studio for checking newspaper upload by anonymous user in his google drive, it opens the pdf file but it is not able to download the pdf file in storage. I don't know whats the wrong with it... following is my code, I created this on my own interest to reading newspaper offline by downloading the pdf. But this only displays the pdf , unable to download it.

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>

<uses-sdk android:minSdkVersion="10" />

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"></uses-permission>
<uses-permission android:name="android.permission.INTERNET"></uses-permission>
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"></uses-permission>
<uses-permission android:name="android.permission.READ_PHONE_STATE"></uses-permission>


<application
    android:allowBackup="true"
    android:icon="@mipmap/ic_launcher"
    android:label="@string/app_name"
    android:supportsRtl="true"
    android:theme="@style/AppTheme">
    <activity android:name=".MainActivity">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.DEFAULT" />
        </intent-filter>
    </activity>
    <activity android:name=".WelcomeActivity">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
</application>

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout>

<WebView
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:id="@+id/webView"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true"
    android:layout_alignParentTop="true" />
</RelativeLayout>

MainActivity.java

public class MainActivity extends AppCompatActivity {

    private WebView mWebView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mWebView = (WebView) findViewById(R.id.webView);
        WebSettings webSettings=mWebView.getSettings();
        webSettings.setJavaScriptEnabled(true);
        mWebView.loadUrl("https://newspaper.wordpress.com/");
        mWebView.setWebViewClient(new WebViewClient());//prevents url in another browser
    }
    @Override
    public void onBackPressed() {
        if(mWebView.canGoBack()){
             mWebView.goBack();
        } else {
            super.onBackPressed();
        }
    }
}