导入依赖包

implementation 'org.xutils:xutils:3.5.0'
implementation  'es.voghdev.pdfviewpager:library:1.0.3'；

如果你用到了了PhotoView或者commit451，因为他们之间有重复的包冲突，所以需要改为：

implementation 'org.xutils:xutils:3.5.0'
    implementation('es.voghdev.pdfviewpager:library:1.0.3') {
        exclude group: 'com.commit451', module: 'PhotoView'
    }

XML文件：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="50dp"
        android:background="@color/colorBlue">


        <ImageView
            android:id="@+id/back"
            android:layout_width="wrap_content"
            android:layout_height="match_parent"
            android:padding="15dp"
            android:src="@mipmap/layout_back" />

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="match_parent"
            android:layout_centerInParent="true"
            android:gravity="center"
            android:text="PDF查看"
            android:textColor="@color/white"
            android:textSize="18sp" />

    </RelativeLayout>

    <View
        android:layout_width="match_parent"
        android:layout_height="0.1dp"
        android:background="@color/gray" />


    <RelativeLayout
        android:id="@+id/remote_pdf_root"
        android:layout_width="match_parent"
        android:layout_height="match_parent">


        <es.voghdev.pdfviewpager.library.PDFViewPager
            android:id="@+id/pdfViewPager"
            android:layout_width="match_parent"
            android:layout_height="match_parent" />

    </RelativeLayout>

    <ProgressBar
        android:id="@+id/pb_bar"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerInParent="true"
        android:layout_gravity="center" />

</LinearLayout>

Activity代码：

import android.os.Bundle;
import android.view.View;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.ProgressBar;
import android.widget.RelativeLayout;
import java.net.URLEncoder;
import butterknife.BindView;
import butterknife.ButterKnife;
import butterknife.OnClick;
import es.voghdev.pdfviewpager.library.PDFViewPager;
import es.voghdev.pdfviewpager.library.RemotePDFViewPager;
import es.voghdev.pdfviewpager.library.adapter.PDFPagerAdapter;
import es.voghdev.pdfviewpager.library.remote.DownloadFile;
import es.voghdev.pdfviewpager.library.util.FileUtil;
import io.reactivex.functions.Consumer;

public class HTDetailActivity extends Activity implements DownloadFile.Listener{

    @BindView(R.id.htdetail_back)
    ImageView contractBack;
    @BindView(R.id.pdfViewPager)
    PDFViewPager pdfViewPager;
    @BindView(R.id.remote_pdf_root)
    RelativeLayout remotePdfRoot;
    @BindView(R.id.pb_bar)
    ProgressBar pbBar;
    private RemotePDFViewPager remotePDFViewPager;
    private PDFPagerAdapter adapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_detail);
        ButterKnife.bind(this);
     //这里的url传文件的地址, 比如: http://www.baidu.com/xxx.pdf    可以把这一句放到查看按钮的点击事件里
        setDownloadListener(url); 
    }

    /*设置监听*/
    protected void setDownloadListener(String url) {
        final DownloadFile.Listener listener = this;
        remotePDFViewPager = new RemotePDFViewPager(this,url, listener);
        remotePDFViewPager.setId(R.id.pdfViewPager);
    }

    /*加载成功调用*/
    @Override
    public void onSuccess(String url, String destinationPath) {
        pbBar.setVisibility(View.GONE);
        adapter = new PDFPagerAdapter(this, FileUtil.extractFileNameFromURL(url));
        remotePDFViewPager.setAdapter(adapter);
        updateLayout();
    }

    /*更新视图*/
    private void updateLayout() {
        remotePdfRoot.removeAllViewsInLayout();
        remotePdfRoot.addView(remotePDFViewPager, LinearLayout.LayoutParams.MATCH_PARENT,
                LinearLayout.LayoutParams.WRAP_CONTENT);
    }

    /*加载失败调用*/
    @Override
    public void onFailure(Exception e) {
        pbBar.setVisibility(View.GONE);
        ToastUtil.showToast(this, "数据加载错误");
    }

    @Override
    public void onProgressUpdate(int progress, int total) {
    }

  
    @OnClick(R.id.htdetail_back)
    public void onViewClicked() {
        finish();
    }

}

欢迎指正，谢谢大家！