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(reason instanceof InvalidPDFException).toEqual(true);
        expect(reason.message).toEqual(
          "The PDF file is empty, i.e. its size is zero bytes."
        );
      }
      await loadingTask.destroy();
    });
    it("checks that `docId`s are unique and increasing", async function () {
      const loadingTask1 = getDocument(basicApiGetDocumentParams);
      expect(loadingTask1 instanceof PDFDocumentLoadingTask).toEqual(true);
      await loadingTask1.promise;
      const docId1 = loadingTask1.docId;
      const loadingTask2 = getDocument(basicApiGetDocumentParams);
      expect(loadingTask2 instanceof PDFDocumentLoadingTask).toEqual(true);
      await loadingTask2.promise;
      const docId2 = loadingTask2.docId;
      expect(docId1).not.toEqual(docId2);
      const docIdRegExp = /^d(\d+)$/,
        docNum1 = docIdRegExp.exec(docId1)?.[1],
        docNum2 = docIdRegExp.exec(docId2)?.[1];
      expect(+docNum1).toBeLessThan(+docNum2);
      await Promise.all([loadingTask1.destroy(), loadingTask2.destroy()]);
    });
  });
  describe("PDFWorker", function () {
    it("worker created or destroyed", async function () {
      if (isNodeJS) {
        pending("Worker is not supported in Node.js.");
      }
      const worker = new PDFWorker({ name: "test1" });