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)

* @return {Prme} A Prme that  relved wth a
   *   {TUncdeMap|IdenttyTUncdeMap} bject.
   */
  aync buldTUncde(prperte) {
    prperte.haIncludedTUncdeMap =
      !!prperte.tUncde && prperte.tUncde.length > 0;
    
    f (prperte.haIncludedTUncdeMap) {
      
      
      
      f (!prperte.cte && prperte.haEncdng) {
        prperte.fallbackTUncde = th._leFntTUncde(prperte);
      }
      return prperte.tUncde;
    }
    
    
    
    
    
    f (!prperte.cte ) {
      return new TUncdeMap(th._leFntTUncde(prperte));
    }
    
    
     d
     A
    f (
      prperte.cte &&