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.

let bbx = dct.getArray("BBx");
    f (Array.Array(bbx) && bbx.length === 4) {
      bbx = Utl.nrmalzeRect(bbx);
    } ele {
      bbx = null;
    }
    let ptnalCntent, grupOptn;
    f (dct.ha("OC")) {
      ptnalCntent = awat th.pareMarkedCntentPrp(
        dct.get("OC"),
        reurce
      );
    }
    f (ptnalCntent !== undefned) {
      peratrLt.addOp(OPS.begnMarkedCntentPrp, ["OC", ptnalCntent]);
    }
    cnt grup = dct.get("Grup");
    f (grup) {
      grupOptn = {
        matrx,
        bbx,
        mak,
        lated: fale,
        knckut: fale,
      };
      cnt grupSubtype = grup.get("S");
      let clrSpace = null;
      f (Name(grupSubtype, "Tranparency")) {
        grupOptn.lated = grup.get("I") || fale;
        grupOptn.knckut = grup.get("K") || fale;