How to open/display documents(.pdf, .doc) without external app?

I think you should use custom library for getting that done .See this and this

But there is a way for displaying PDF with out calling another application

This is a way for showing PDF in android app that is embedding the PDF document to android webview using support from http://docs.google.com/viewer

pseudo

String doc="<iframe src='http://docs.google.com/viewer?url=+location to your PDF File+' 
              width='100%' height='100%' 
              style='border: none;'></iframe>";

a sample is is shown below

 String doc="<iframe src='http://docs.google.com/viewer?url=http://www.iasted.org/conferences/formatting/presentations-tips.ppt&embedded=true' 
              width='100%' height='100%' 
              style='border: none;'></iframe>";

Code

    WebView  wv = (WebView)findViewById(R.id.webView); 
    wv.getSettings().setJavaScriptEnabled(true);
    wv.getSettings().setPluginsEnabled(true);
    wv.getSettings().setAllowFileAccess(true);
    wv.loadUrl(doc);
    //wv.loadData( doc, "text/html",  "UTF-8");

and in manifest provide

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

See this

Caution : I am not aware of compatibility issues with various android versions

In this approach the drawback is you need internet connectivity . But i think it satisfy your need

EDIT Try this as src for iframe

src="http://docs.google.com/gview?embedded=true&url=http://www.pc-hardware.hu/PDF/konfig.pdf"

try wv.loadData( doc , "text/html", "UTF-8"); . Both works for me

Download the source code from here (Display PDF file inside my android application)

Add this dependency in your Grade:

compile 'com.github.barteksc:android-pdf-viewer:2.0.3'

activity_main.xml

<RelativeLayout android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#ffffff"
    xmlns:android="http://schemas.android.com/apk/res/android" >

    <TextView
        android:layout_width="match_parent"
        android:layout_height="40dp"
        android:background="@color/colorPrimaryDark"
        android:text="View PDF"
        android:textColor="#ffffff"
        android:id="@+id/tv_header"
        android:textSize="18dp"
        android:gravity="center"></TextView>

    <com.github.barteksc.pdfviewer.PDFView
        android:id="@+id/pdfView"
        android:layout_below="@+id/tv_header"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>


    </RelativeLayout>

MainActivity.java

package pdfviewer.pdfviewer;

import android.app.Activity;
import android.database.Cursor;
import android.net.Uri;
import android.provider.OpenableColumns;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.ImageView;
import android.widget.RelativeLayout;

import com.github.barteksc.pdfviewer.PDFView;
import com.github.barteksc.pdfviewer.listener.OnLoadCompleteListener;
import com.github.barteksc.pdfviewer.listener.OnPageChangeListener;
import com.github.barteksc.pdfviewer.scroll.DefaultScrollHandle;
import com.shockwave.pdfium.PdfDocument;

import java.util.List;

public class MainActivity extends Activity implements OnPageChangeListener,OnLoadCompleteListener{
    private static final String TAG = MainActivity.class.getSimpleName();
    public static final String SAMPLE_FILE = "android_tutorial.pdf";
    PDFView pdfView;
    Integer pageNumber = 0;
    String pdfFileName;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);


        pdfView= (PDFView)findViewById(R.id.pdfView);
        displayFromAsset(SAMPLE_FILE);
    }

    private void displayFromAsset(String assetFileName) {
        pdfFileName = assetFileName;

        pdfView.fromAsset(SAMPLE_FILE)
                .defaultPage(pageNumber)
                .enableSwipe(true)

                .swipeHorizontal(false)
                .onPageChange(this)
                .enableAnnotationRendering(true)
                .onLoad(this)
                .scrollHandle(new DefaultScrollHandle(this))
                .load();
    }


    @Override
    public void onPageChanged(int page, int pageCount) {
        pageNumber = page;
        setTitle(String.format("%s %s / %s", pdfFileName, page + 1, pageCount));
    }


    @Override
    public void loadComplete(int nbPages) {
        PdfDocument.Meta meta = pdfView.getDocumentMeta();
        printBookmarksTree(pdfView.getTableOfContents(), "-");

    }

    public void printBookmarksTree(List<PdfDocument.Bookmark> tree, String sep) {
        for (PdfDocument.Bookmark b : tree) {

            Log.e(TAG, String.format("%s %s, p %d", sep, b.getTitle(), b.getPageIdx()));

            if (b.hasChildren()) {
                printBookmarksTree(b.getChildren(), sep + "-");
            }
        }
    }

}

Thanks!

Well, I think below is the solution

 String doc="<iframe src='http://docs.google.com/viewer?url=http://www.example.com/yourfile.pdf&embedded=true' width='100%' height='100%'  style='border: none;'></iframe>";


    WebView  wv = (WebView)findViewById(R.id.wv);
    wv.setVisibility(WebView.VISIBLE);
    wv.getSettings().setJavaScriptEnabled(true);
    wv.getSettings().setAllowFileAccess(true);
    wv.getSettings().setPluginState(WebSettings.PluginState.ON);  
    wv.setWebViewClient(new Callback()); 
    wv.loadData(doc, "text/html", "UTF-8");   

Hoping this will help you :)

Above answers that are dependent on google docs will work only when you have internet connection. A better option would be to use Android PdfRenderer class.

You can try sample app here.