POM依赖

        <dependency>
            <groupId>org.apache.pdfbox</groupId>
            <artifactId>fontbox</artifactId>
            <version>2.0.9</version>
        </dependency>
        <dependency>
            <groupId>org.apache.pdfbox</groupId>
            <artifactId>pdfbox</artifactId>
            <version>2.0.9</version>
        </dependency>

代码

package com.example.demo;

import org.apache.pdfbox.pdmodel.PDDocument;
import org.apache.pdfbox.rendering.PDFRenderer;

import javax.imageio.ImageIO;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;

public class Demo1 {
  public static void main(String[] args) {
    pdf2png("D:","111","png");
  }

    /**
     * 转换全部的pdf
     * @param fileAddress 文件地址
     * @param filename PDF文件名
     * @param type 图片类型
     */
    public static void pdf2png(String fileAddress,String filename,String type) {
        // 将pdf装图片 并且自定义图片得格式大小
        File file = new File(fileAddress+"\\"+filename+".pdf");
        try {
            PDDocument doc = PDDocument.load(file);
            PDFRenderer renderer = new PDFRenderer(doc);
            int pageCount = doc.getNumberOfPages();
            for (int i = 0; i < pageCount; i++) {
                //注意：DPI决定转之后图片的清晰度
                BufferedImage image = renderer.renderImageWithDPI(i, 300); // Windows native DPI
                // BufferedImage srcImage = resize(image, 240, 240);//产生缩略图
                ImageIO.write(image, type, new File(fileAddress+"\\"+filename+"_"+(i+1)+"."+type));
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}