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)

Object.assign(styleCache, value.styles);
          this._processItems(value.items, styleCache);
          pump();
        }, capability.reject);
      };
      this._reader = this._textContentStream.getReader();
      pump();
    } else {
      throw new Error(
        'Neither "textContent" nor "textContentStream" parameters specified.'
      );
    }
    capability.promise.then(() => {
      styleCache = null;
      if (!timeout) {
        
        render(this);
      } else {
        
        this._renderTimer = setTimeout(() => {
          render(this);
          this._renderTimer = null;
        }, timeout);
      }
    }, this._capability.reject);
  }
  /**
   * @param {boolean} [expandDivs]
   */
  expandTextDivs(expandDivs = false) {