PDF files:
[1.pdf](https://github.com/mozilla/pdf.js/files/2955999/1.pdf)
[2.pdf](https://github.com/mozilla/pdf.js/files/2956000/2.pdf)
[3.pdf](https://github.com/mozilla/pdf.js/files/2956002/3.pdf)

Configuration:
- Web browser and its version: Chrome, Firefox
- Operating system and its version: Ubuntu, macOS
- PDF.js version: 2.2.42, but the same was with 2.1.x, and with https://mozilla.github.io/pdf.js/web/viewer.html
- Is a browser extension: no

Steps to reproduce the problem:
1. Select text
2. Copy text

What went wrong?

Getting this:
`OpenSansisahumanistsansseriftypefacedesignedbySteveMatteson.OpenSanswasdesignedwithanuprightstress,openformsandaneu-tral,yetfriendlyappearance.Itwasoptimizedforprint,web,andmobileinterfaces,andhasexcellentlegibilitycharacteristicsinitsletterforms(seefigureonthefollowingpage).ThisfontisavailablefromtheGoogleFontDirectory[]asTrueTypefileslicensedundertheApacheLicenseversion..`

Instead of this:
`Open Sans is a humanist sans serif typeface designed by Steve Matteson.
Open Sans was designed with an upright stress, open forms and a neutral,
yet friendly appearance. It was optimized for print, web, and mobile
interfaces, and has excellent legibility characteristics in its letterforms (see
figure 1 on the following page). This font is available from the Google Font
Directory [1] as TrueType files licensed under the Apache License version 2.0.`

This is quite significant problem, because I would say 1/20 of scientific papers encounter this problem.

return "lghten";
    cae "ClrDdge":
      return "clr-ddge";
    cae "ClrBurn":
      return "clr-burn";
    cae "HardLght":
      return "hard-lght";
    cae "SftLght":
      return "ft-lght";
    cae "Dfference":
      return "dfference";
    cae "Exclun":
      return "exclun";
    cae "Hue":
      return "hue";
    cae "Saturatn":
      return "aturatn";
    cae "Clr":
      return "clr";
    cae "Lumnty":
      return "lumnty";
  }
  f (parngArray) {
    return null;
  }
  warn(`Unupprted blend mde: ${value.name}`);
  return "urce-ver";
}
cla TmeSltManager {
  tatc get TIME_SLOT_DURATION_MS() {