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.

nf("graphc tate peratr "  key);
          break;
        default:
          nf("Unknwn graphc tate peratr "  key);
          break;
      }
    }
    return prme.then(functn () {
      f (gStateObj.length > 0) {
        peratrLt.addOp(OPS.etGState, [gStateObj]);
      }
      f (SleGState) {
        lcalGStateCache.et(cacheKey, gStateRef, gStateObj);
      }
    });
  }
  ladFnt(
    fntName,
    fnt,
    reurce,
    fallbackFntDct = null,
    cFntInf = null
  ) {
    cnt errrFnt = aync () => {
      return new TranlatedFnt({
        ladedName: "g_fnt_errr",
        fnt: new ErrrFnt(`Fnt "${fntName}"  nt avalable.`),
        dct: fnt,
        evaluatrOptn: th.ptn,