You can download the source from here(Display PDF file inside my android application)

Add this dependency in your gradle file:

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.os.Bundle;
import android.util.Log;
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 + "-");
            }
        }
    }

}

You can view a pdf file in an android project in different ways. I will describe some of them here-

1. Using Library: Steps are below:

Installation Add to build.gradle: implementation 'com.github.barteksc:android-pdf-viewer:2.8.2'
ProGuard If you are using ProGuard, add following rule to proguard config file:
-keep class com.shockwave.**
Include PDFView in your layout
<com.github.barteksc.pdfviewer.PDFView android:id="@+id/pdfView" android:layout_width="match_parent" android:layout_height="match_parent"/>
Further link is here
2. Load pdf url into webview:

webview = (WebView)findViewById(R.id.webview);
    progressbar = (ProgressBar) findViewById(R.id.progressbar);
    webview.getSettings().setJavaScriptEnabled(true);
    String filename = file_url_with_name;
    webview.loadUrl(file_url + filename);

    webview.setWebViewClient(new WebViewClient() {

        public void onPageFinished(WebView view, String url) {
            // do your stuff here
            progressbar.setVisibility(View.GONE);
        }
    });

3. Manually show PDF file into Imageview

// Example for creating manual PDF viewer into imageview used butterknife view binding<br/>

public class PdfRenderActivity extends AppCompatActivity {

    @BindView(R.id.pdf_image) ImageView imageViewPdf;
    @BindView(R.id.button_pre_doc) FloatingActionButton prePageButton;
    @BindView(R.id.button_next_doc) FloatingActionButton nextPageButton;

    private static final String FILENAME = "report.pdf";

    private int pageIndex;
    private PdfRenderer pdfRenderer;
    private PdfRenderer.Page currentPage;
    private ParcelFileDescriptor parcelFileDescriptor;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_pdf_render);
        ButterKnife.bind(this);
        pageIndex = 0;
    }

    @RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)
    @Override
    protected void onStart() {
        super.onStart();
        try {
            openRenderer(getApplicationContext());
            showPage(pageIndex);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    @RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)
    @Override
    public void onStop() {
        try {
            closeRenderer();
        } catch (IOException e) {
            e.printStackTrace();
        }
        super.onStop();
    }

    @RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)
    @OnClick(R.id.button_pre_doc)
    public void onPreviousDocClick(){
        showPage(currentPage.getIndex() - 1);
    }

    @RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)
    @OnClick(R.id.button_next_doc)
    public void onNextDocClick(){
        showPage(currentPage.getIndex() + 1);
    }

    @RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)
    private void openRenderer(Context context) throws IOException {
        // In this sample, we read a PDF from the assets directory.
        File file = new File(context.getCacheDir(), FILENAME);
        if (!file.exists()) {
            // Since PdfRenderer cannot handle the compressed asset file directly, we copy it into
            // the cache directory.
            InputStream asset = context.getAssets().open(FILENAME);
            FileOutputStream output = new FileOutputStream(file);
            final byte[] buffer = new byte[1024];
            int size;
            while ((size = asset.read(buffer)) != -1) {
                output.write(buffer, 0, size);
            }
            asset.close();
            output.close();
        }
        parcelFileDescriptor = ParcelFileDescriptor.open(file, ParcelFileDescriptor.MODE_READ_ONLY);
        // This is the PdfRenderer we use to render the PDF.
        if (parcelFileDescriptor != null) {
            pdfRenderer = new PdfRenderer(parcelFileDescriptor);
        }
    }

    @RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)
    private void closeRenderer() throws IOException {
        if (null != currentPage) {
            currentPage.close();
        }
        pdfRenderer.close();
        parcelFileDescriptor.close();
    }

    @RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)
    private void showPage(int index) {
        if (pdfRenderer.getPageCount() <= index) {
            return;
        }
        // Make sure to close the current page before opening another one.
        if (null != currentPage) {
            currentPage.close();
        }
        // Use `openPage` to open a specific page in PDF.
        currentPage = pdfRenderer.openPage(index);
        // Important: the destination bitmap must be ARGB (not RGB).
        Bitmap bitmap = Bitmap.createBitmap(currentPage.getWidth(), currentPage.getHeight(),
                Bitmap.Config.ARGB_8888);
        // Here, we render the page onto the Bitmap.
        // To render a portion of the page, use the second and third parameter. Pass nulls to get
        // the default result.
        // Pass either RENDER_MODE_FOR_DISPLAY or RENDER_MODE_FOR_PRINT for the last parameter.
        currentPage.render(bitmap, null, null, PdfRenderer.Page.RENDER_MODE_FOR_DISPLAY);
        // We are ready to show the Bitmap to user.
        imageViewPdf.setImageBitmap(bitmap);
        updateUi();
    }

    /**
     * Updates the state of 2 control buttons in response to the current page index.
     */
    @RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)
    private void updateUi() {
        int index = currentPage.getIndex();
        int pageCount = pdfRenderer.getPageCount();
        prePageButton.setEnabled(0 != index);
        nextPageButton.setEnabled(index + 1 < pageCount);
    }

    @RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)
    public int getPageCount() {
        return pdfRenderer.getPageCount();
    }

}

Doc is here