I'd recommend considering MuPDF which has already been ported for use on Android several times without reliance on Java. MuPDF is optimized for lightweight on-screen PDF rendering, making it perfect for mobile use.

Please note that MuPDF and all the derived projects are not suitable for the commercial use and you should consider alternatives if you are not developing an open source GPL project.

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

Use below code for that.

First.java

public class First extends ListActivity {

    String[] pdflist;
    File[] imagelist;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        //setContentView(R.layout.main);

        File images = Environment.getExternalStorageDirectory();
        imagelist = images.listFiles(new FilenameFilter() {
            public boolean accept(File dir, String name) {
                return ((name.endsWith(".pdf")));
            }
        });
        pdflist = new String[imagelist.length];
        for (int i = 0; i < imagelist.length; i++) {
            pdflist[i] = imagelist[i].getName();
        }
        this.setListAdapter(new ArrayAdapter<String>(this,
                android.R.layout.simple_list_item_1, pdflist));
    }

    protected void onListItemClick(ListView l, View v, int position, long id) {
        super.onListItemClick(l, v, position, id);
        String path = imagelist[(int) id].getAbsolutePath();
        openPdfIntent(path);
    }

    private void openPdfIntent(String path) {
        try {
            final Intent intent = new Intent(First.this, Second.class);
            intent.putExtra(PdfViewerActivity.EXTRA_PDFFILENAME, path);
            startActivity(intent);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

Second.java

public class Second extends PdfViewerActivity {

    @Override
    public void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
    }

    public int getPreviousPageImageResource() {
        return R.drawable.left_arrow;
    }

    public int getNextPageImageResource() {
        return R.drawable.right_arrow;
    }

    public int getZoomInImageResource() {
        return R.drawable.zoom_in;
    }

    public int getZoomOutImageResource() {
        return R.drawable.zoom_out;
    }

    public int getPdfPasswordLayoutResource() {
        return R.layout.pdf_file_password;
    }

    public int getPdfPageNumberResource() {
        return R.layout.dialog_pagenumber;
    }

    public int getPdfPasswordEditField() {
        return R.id.etPassword;
    }

    public int getPdfPasswordOkButton() {
        return R.id.btOK;
    }

    public int getPdfPasswordExitButton() {
        return R.id.btExit;
    }

    public int getPdfPageNumberEditField() {
        return R.id.pagenum_edit;
    }
}

And declared both activities into your manifest file.

You can open pdf files using Intents.

File file = new File(Environment.getExternalStorageDirectory().getAbsolutePath()+"/example.pdf");
Intent intent = new Intent(Intent.ACTION_VIEW);
intent.setDataAndType(Uri.fromFile(file), "application/pdf");
intent.setFlags(Intent.FLAG_ACTIVITY_NO_HISTORY);
startActivity(intent);

If you dont like this method, and want to open pdf files inside your application, you can use a custom PDF Viewer.

In your gradle file compile this: 'com.github.barteksc:android-pdf-viewer:2.0.3'

After you sync your project, go to your xml file and add the PDF Viewer.

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

Now in your .java file you will import:

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;

You will Implement two methods: OnPageChangeListener and OnLoadCompleteListener

MAIN CODE:

    public static final String SAMPLE_FILE = "android_tutorial.pdf"; //your file path
    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;
    }
 
 
    @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) {
            if (b.hasChildren()) {
                printBookmarksTree(b.getChildren(), sep + "-");
            }
        }
    }

Thats it!

P.S: First search on google, if you dont find something, write your question!

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