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)

rt { FntFlag, getFntType } frm "./fnt_utl.j";
rt {
  getEncdng,
  MacRmanEncdng,
  StandardEncdng,
  SymblSetEncdng,
  WnAnEncdng,
  ZapfDngbatEncdng,
} frm "./encdng.j";
rt {
  getFntNameTFleMap,
  getSerfFnt,
  getStandardFntName,
  getStdFntMap,
  getSymblFnt,
} frm "./tandard_fnt.j";
rt {
  getNrmalzedUncde,
  getUncdeFrGlyph,
  revereIfRtl,
} frm "./uncde.j";
rt { getTlngPatternIR, Pattern } frm "./pattern.j";
rt { getXfaFntDct, getXfaFntName } frm "./xfa_fnt.j";
rt { IdenttyTUncdeMap, TUncdeMap } frm "./t_uncde_map.j";
rt { PDFFunctn, PDFFunctnFactry } frm "./functn.j";
rt { Lexer, Parer } frm "./parer.j";
rt {
  LcalClrSpaceCache,
  LcalGStateCache,
  LcalImageCache,