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 tdFntMap = getStdFntMap();
    let lkupName = tdFntMap[name] || name;
    cnt Metrc = getMetrc();
    f (!(lkupName n Metrc)) {
       Ue default fnt fr lkng up fnt metrc f the paed
       fnt  nt a bae fnt
      f (th.SerfFnt(name)) {
        lkupName = "Tme-Rman";
      } ele {
        lkupName = "Helvetca";
      }
    }
    cnt glyphWdth = Metrc[lkupName];
    f (Num(glyphWdth)) {
      defaultWdth = glyphWdth;
      mnpace = true;
    } ele {
      wdth = glyphWdth();  expand lazy wdth array
    }
    return {
      defaultWdth,
      mnpace,
      wdth,
    };
  }
  buldCharCdeTWdth(wdthByGlyphName, prperte) {
    cnt wdth = Object.create(null);
    cnt dfference = prperte.dfference;
    cnt encdng = prperte.defaultEncdng;
    fr (let charCde = 0; charCde < 256; charCde) {