<dependency>
        <groupId>com.itextpdf</groupId>
        <artifactId>itextpdf</artifactId>
        <version>5.5.13</version>
    </dependency>

import com.itextpdf.text.Document;
import com.itextpdf.text.DocumentException;
import com.itextpdf.text.Image;
import com.itextpdf.text.PageSize;
import com.itextpdf.text.pdf.PdfWriter;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

public class ImageToPDF {
    public static void main(String[] arg){
        //创建个存放图片地址的集合
        List<String> imageUrlList = new ArrayList();
        //添加图片地址到集合
        imageUrlList.add("/Users/mac/Desktop/WechatIMG18.png");
        //存放pdf文件的路径
        String pdfUrl = "/Users/mac/Desktop/123.pdf";
        imgOfPdf(imageUrlList,pdfUrl);
    }
    public static void imgOfPdf(List<String> imageUrlList,String pdfUrl) {
        try {
            File file = PdfUtilImg(imageUrlList, pdfUrl);//生成pdf
            file.createNewFile();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public static File PdfUtilImg(List<String> imageUrllist, String pdfUrl) {
        //new一个pdf文档
        Document doc = new Document(PageSize.A4, 20, 20, 20, 20);
        try {
            //pdf写入
            PdfWriter.getInstance(doc, new FileOutputStream(pdfUrl));
            //打开文档
            doc.open();
            //遍历集合，将图片放在pdf文件
            for (int i = 0; i < imageUrllist.size(); i++) {
                //在pdf创建一页   主：此处为每一张图片是pdf文件的一页
                doc.newPage();
                //通过文件路径获取image
                Image png1 = Image.getInstance(imageUrllist.get(i));
                float heigth = png1.getHeight();
                float width = png1.getWidth();
                int percent = getPercent2(heigth, width);
                png1.setAlignment(Image.MIDDLE);
                // 表示是原来图像的比例;
                png1.scalePercent(percent+3);
                doc.add(png1);
            }
            doc.close();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (DocumentException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        //输出流
        File mOutputPdfFile = new File(pdfUrl);
        if (!mOutputPdfFile.exists()) {
            mOutputPdfFile.deleteOnExit();
            return null;
        }
        //反回文件输出流
        return mOutputPdfFile;
    }

    public static int getPercent(float h, float w) {
        int p = 0;
        float p2 = 0.0f;
        if (h > w) {
            p2 = 297 / h * 100;
        } else {
            p2 = 210 / w * 100;
        }
        p = Math.round(p2);
        return p;
    }

    public static int getPercent2(float h, float w) {
        int p = 0;
        float p2 = 0.0f;
        p2 = 530 / w * 100;
        p = Math.round(p2);
        return p;
    }
}