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)

let totalPages = matchesPerPage.length;
    for (let i = totalPages - 1; i >= 0; i--) {
      if (matchesPerPage[i] > 0) {
        totalPages = i + 1;
        break;
      }
    }
    const totalMatches = matchesPerPage.reduce((a, b) => {
      return a + b;
    });
    eventBus.on(
      "updatefindmatchescount",
      function onUpdateFindMatchesCount(evt) {
        if (pdfFindController.pageMatches.length !== totalPages) {
          return;
        }
        eventBus.off("updatefindmatchescount", onUpdateFindMatchesCount);
        expect(evt.matchesCount.total).toBe(totalMatches);
        for (let i = 0; i < totalPages; i++) {
          expect(pdfFindController.pageMatches[i].length).toEqual(
            matchesPerPage[i]
          );
        }
        expect(pdfFindController.selected.pageIdx).toEqual(
          selectedMatch.pageIndex
        );
        expect(pdfFindController.selected.matchIdx).toEqual(
          selectedMatch.matchIndex