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)

const data = await Promise.all([
        loadingTask1.promise,
        loadingTask2.promise,
      ]);
      const fingerprints1 = data[0].fingerprints;
      const fingerprints2 = data[1].fingerprints;
      expect(fingerprints1).not.toEqual(fingerprints2);
      expect(fingerprints1).toEqual(["2f695a83d6e7553c24fc08b7ac69712d", null]);
      expect(fingerprints2).toEqual(["04c7126b34a46b6d4d6e7a1eff7edcb6", null]);
      await Promise.all([loadingTask1.destroy(), loadingTask2.destroy()]);
    });
    it("write a value in an annotation, save the pdf and load it", async function () {
      let loadingTask = getDocument(buildGetDocumentParams("evaljs.pdf"));
      let pdfDoc = await loadingTask.promise;
      const value = "Hello World";
      pdfDoc.annotationStorage.setValue("55R", { value });
      const data = await pdfDoc.saveDocument();
      await loadingTask.destroy();
      loadingTask = getDocument(data);
      pdfDoc = await loadingTask.promise;
      const pdfPage = await pdfDoc.getPage(1);
      const annotations = await pdfPage.getAnnotations();
      const field = annotations.find(annotation => annotation.id === "55R");
      expect(!!field).toEqual(true);
      expect(field.fieldValue).toEqual(value);
      await loadingTask.destroy();
    });
    describe("Cross-origin", function () {
      let loadingTask;
      function _checkCanLoad(expectSuccess, filename, options) {