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)

await worker.promise;
      expect(worker.name).toEqual("test1");
      expect(!!worker.port).toEqual(true);
      expect(worker.destroyed).toEqual(false);
      expect(!!worker._webWorker).toEqual(true);
      expect(worker.port === worker._webWorker).toEqual(true);
      worker.destroy();
      expect(!!worker.port).toEqual(false);
      expect(worker.destroyed).toEqual(true);
    });
    it("worker created or destroyed by getDocument", async function () {
      if (isNodeJS) {
        pending("Worker is not supported in Node.js.");
      }
      const loadingTask = getDocument(basicApiGetDocumentParams);
      let worker;
      loadingTask.promise.then(function () {
        worker = loadingTask._worker;
        expect(!!worker).toEqual(true);
      });
      const destroyPromise = loadingTask.promise.then(function () {
        return loadingTask.destroy();
      });
      await destroyPromise;
      const destroyedWorker = loadingTask._worker;
      expect(!!destroyedWorker).toEqual(false);
      expect(worker.destroyed).toEqual(true);
    });
    it("worker created and can be used in getDocument", async function () {
      if (isNodeJS) {