Attach (recommended) or Link to PDF file here:

Configuration:
- Web browser and its version: Version 81.0.4044.138 (Official Build) (32-bit)
- Operating system and its version: Windows 10
- PDF.js version: latest
- Is a browser extension: no

Steps to reproduce the problem:

1. Open https://mozilla.github.io/pdf.js/web/viewer.html
2. Open the provided document
3. ctrl + F  and search for 'costs' .
4. Search for 'costs' - match NOT found.
5. Click the 'Download' and open the file in Adobe Reader, and search for costs - match is found.

What is the expected behavior? (add screenshot)
The word 'costs' to be returned by search

What went wrong? (add screenshot)
No results found

Link to a viewer (if hosted on a site other than mozilla.github.io/pdf.js or as Firefox/Chrome extension):  https://mozilla.github.io/pdf.js/web/viewer.html
[2001_IESC_63_5_v6.pdf](https://github.com/mozilla/pdf.js/files/4644486/2001_IESC_63_5_v6.pdf)

expect(
        worker1.port !== worker2.port &&
          worker1.port !== worker3.port &&
          worker2.port !== worker3.port
      ).toEqual(true);
      worker1.destroy();
      worker2.destroy();
      worker3.destroy();
    });
    it("gets current workerSrc", function () {
      if (isNodeJS) {
        pending("Worker is not supported in Node.js.");
      }
      const workerSrc = PDFWorker.workerSrc;
      expect(typeof workerSrc).toEqual("string");
      expect(workerSrc).toEqual(GlobalWorkerOptions.workerSrc);
    });
  });
  describe("PDFDocument", function () {
    let pdfLoadingTask, pdfDocument;
    beforeAll(async function () {
      pdfLoadingTask = getDocument(basicApiGetDocumentParams);
      pdfDocument = await pdfLoadingTask.promise;
    });
    afterAll(async function () {
      await pdfLoadingTask.destroy();
    });
    it("gets number of pages", function () {
      expect(pdfDocument.numPages).toEqual(3);
    });