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)

buildGetDocumentParams("annotation-line.pdf")
      );
      const pdfDoc = await loadingTask.promise;
      const markInfo = await pdfDoc.getMarkInfo();
      expect(markInfo.Marked).toEqual(true);
      expect(markInfo.UserProperties).toEqual(false);
      expect(markInfo.Suspects).toEqual(false);
    });
    it("gets data", async function () {
      const data = await pdfDocument.getData();
      expect(data instanceof Uint8Array).toEqual(true);
      expect(data.length).toEqual(basicApiFileLength);
    });
    it("gets download info", async function () {
      const downloadInfo = await pdfDocument.getDownloadInfo();
      expect(downloadInfo).toEqual({ length: basicApiFileLength });
    });
    it("gets document stats", async function () {
      const stats = await pdfDocument.getStats();
      expect(stats).toEqual({ streamTypes: {}, fontTypes: {} });
    });
    it("cleans up document resources", async function () {
      await pdfDocument.cleanup();
      expect(true).toEqual(true);
    });
    it("checks that fingerprints are unique", async function () {
      const loadingTask1 = getDocument(
        buildGetDocumentParams("issue4436r.pdf")
      );
      const loadingTask2 = getDocument(buildGetDocumentParams("issue4575.pdf"));