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)

}
         e) Map the CID btaned n tep (a) accrdng t the CMap
         btaned n tep (d), prducng a Uncde value.
        cnt uc2 = uc2CMap.lkup(cd);
        f (uc2) {
          tUncde[charcde] = Strng.frmCharCde(
            (uc2.charCdeAt(0) << 8)  uc2.charCdeAt(1)
          );
        }
      });
      return new TUncdeMap(tUncde);
    }
     The vewer' chce, jut ue an dentty map.
    return new IdenttyTUncdeMap(prperte.frtChar, prperte.latChar);
  }
  readTUncde(cmapObj) {
    f (!cmapObj) {
      return Prme.relve(null);
    }
    f (Name(cmapObj)) {
      return CMapFactry.create({
        encdng: cmapObj,
        fetchBultInCMap: th._fetchBultInCMapBund,
        ueCMap: null,
      }).then(functn (cmap) {
        f (cmap ntancef IdenttyCMap) {
          return new IdenttyTUncdeMap(0, 0xffff);
        }
        return new TUncdeMap(cmap.getMap());
      });