一、下载插件

 npm install pdf-lib@1.17.1
 npm install pdfjs-dist@2.16.105

二、在页面中引入插件

 let pdfjsLib = require("pdfjs-dist/legacy/build/pdf.js");
 import workerSrc from "pdfjs-dist/legacy/build/pdf.worker.entry";
 pdfjsLib.GlobalWorkerOptions.workerSrc = workerSrc;
 import { PDFDocument, rgb } from 'pdf-lib'

三、页面中的使用

<input type="file" class="file" id="file" ref="fielinput" @change="uploadFile" />
async uploadFile() {
  let fileInput = this.$refs.fielinput;
  let fileData = fileInput.files[0];

  this.fileName = fileData.name;
  let reader = new FileReader(); //文件读取
  reader.readAsDataURL(fileData); //得到读取的文件
  reader.onload = async () => { //文件加载
    let data = atob(
      reader.result.substring(reader.result.indexOf(",") + 1)
    );
    this.loadPdfData(data);
  };
},
loadPdfData(data) {
  // 引入pdf.js的字体
  let CMAP_URL = "https://unpkg.com/pdfjs-dist@2.0.943/cmaps/";
  // 读取base64的pdf流文件 返回pdf实例对象
  this.pdfData = pdfjsLib.getDocument({
    data: data, // PDF base64编码
    cMapUrl: CMAP_URL,
    cMapPacked: true,
  });
  // this.pdfData = pdfjsLib.getDocument(this.url)
},
// 根据页码渲染相应的PDF
renderPage() { //num传入页 返回对应页的pdf数据
  this.pdfData.promise.then((pdf) => {

    this.pdfPageNumber = pdf.numPages;

    for (let i = 1; i <= this.pdfPageNumber; i++) {
      pdf.getPage(i).then((page) => {
        let canvas = document.createElement("canvas");
        let viewport = page.getViewport({ scale: 3 }); //获取窗口属性
        canvas.height = viewport.height;
        canvas.width = viewport.width;
        let ctx = canvas.getContext("2d");
        let renderContext = {
          canvasContext: ctx,
          viewport: viewport,
        };
        this.$refs.canvasBox.appendChild(canvas);
        let renderTask = page.render(renderContext)
        renderTask.promise.then(() => {
          if (this.pdfPageNumber == i) {
            this.canvasFile();
          }
        })
      });
    }
  });
},
 //canvas 文件数据 下载
 async canvasFile() {
  let childNodes = this.$refs.canvasBox.childNodes;
  // 创建PDF文档
  const pdfDoc = await PDFDocument.create();
  let y = 0;
  for (let i = 0; i < childNodes.length; i++) {
    // 读取PNG图片
    let dataUrl = childNodes[i].toDataURL('image/png')
    const img = await pdfDoc.embedPng(dataUrl);
    const page = pdfDoc.addPage([595.28, 841.89])
    const { width, height } = img.scaleToFit(595.28, 841.89);
    page.drawImage(img, {
      x: 0,
      y: 0,
      width: width,
      height: height,
    });

    page.drawText('amy', {
      x: width - 50,
      y: 40,
      size: 16,
      color: rgb(0.46, 0.53, 0.6),
      opacity: 1,
    })
  }
},

四、将签章后的PDF文档下载到本地

   const pdfBytes = await pdfDoc.save()

  1.文件下载插件方式一
  download(pdfBytes, "pdf-lib_image_embedding_example.pdf", "application/pdf");

  2.文件下载插件方式二
  let blobData = new Blob([pdfBytes], { type: "application/pdf;Base64" });
  let a = document.createElement("a");
  a.target = "_blank";
  a.href = window.URL.createObjectURL(blobData);
  document.body.appendChild(a);
  a.click();
  document.body.removeChild(a);

文件插件链接地址：
https://gitee.com/amysunny/plug-in-unit/tree/master/