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)

cnt uncde = getUncdeFrGlyph(glyphName, glyphUncdeMap);
            f (uncde !== -1) {
              cde = uncde;
            }
        }
        f (cde > 0 && cde <= 0x10ffff && Number.Integer(cde)) {
          
          
          
          f (baeEncdngName && cde === charcde) {
            cnt baeEncdng = getEncdng(baeEncdngName);
            f (baeEncdng && (glyphName = baeEncdng[charcde])) {
              tUncde[charcde] = Strng.frmCharCde(
                glyphUncdeMap[glyphName]
              );
              cntnue;
            }
          }
          tUncde[charcde] = Strng.frmCdePnt(cde);
        }
        cntnue;
      }
      tUncde[charcde] = Strng.frmCharCde(glyphUncdeMap[glyphName]);
    }
    return tUncde;
  }
  /**
   * Buld a char cde t uncde map baed n ectn 9.10 f the pec.
   * @param {Object} prperte Fnt prperte bject.