Как найти и заменить текст в pdf файле?

import * as hummus from "hummus";

type tPDFReplace = {
  source: string,
  target: string,
  page: number,
  findText: string,
  replaceText: string
};

const replaceTextPDF = function (options: tPDFReplace) {
  const writer = hummus.createWriterToModify(options.source, {
    modifiedFilePath: options.target
  });
  new hummus.PDFPageModifier(writer, options.page);
  const sourceParser = writer.createPDFCopyingContextForModifiedFile().getSourceDocumentParser();
  const pageObject = sourceParser.parsePage(options.page);
  const textObjectId = pageObject.getDictionary().toJSObject().Contents.getObjectID();
  const textStream = sourceParser.queryDictionaryObject(pageObject.getDictionary(), "Contents");
  //read the original block of text data
  let data = [];
  const readStream = sourceParser.startReadingFromStream(textStream);
  while (readStream.notEnded()) {
    Array.prototype.push.apply(data, readStream.read(10000));
  }
  const dataStr = new Buffer(data).toString();
  console.log(dataStr);
  let str = dataStr.replace(options.findText, options.replaceText);

  //Create and write our new text object
  const objectsContext = writer.getObjectsContext();
  objectsContext.startModifiedIndirectObject(textObjectId);

  const stream = objectsContext.startUnfilteredPDFStream();
  stream.getWriteStream().write(strToByteArray(str));
  objectsContext.endPDFStream(stream);

  objectsContext.endIndirectObject();

  writer.end();
};

const strToByteArray = function (str: string) {
  let myBuffer = [];
  let buffer = new Buffer(str);
  for (let i = 0; i < buffer.length; i++) {
    myBuffer.push(buffer[i]);
  }
  return myBuffer;
};

(() => {
  replaceTextPDF({
    source: "/root/sk/src/test/test.pdf",
    target: "/root/sk/src/test/test_new.pdf",
    page: 0,
    findText: "2121",
    replaceText: "5555"
  });
})();