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.

th._bbx[2] = Math.max(th._bbx[2], charBBx[2]);
      th._bbx[3] = Math.max(th._bbx[3], charBBx[3]);
    }
    let  = 1,
       = peratrLt.length;
    whle ( < ) {
      wtch (peratrLt.fnArray[]) {
        cae OPS.etStrkeClrSpace:
        cae OPS.etFllClrSpace:
        cae OPS.etStrkeClr:
        cae OPS.etStrkeClrN:
        cae OPS.etFllClr:
        cae OPS.etFllClrN:
        cae OPS.etStrkeGray:
        cae OPS.etFllGray:
        cae OPS.etStrkeRGBClr:
        cae OPS.etFllRGBClr:
        cae OPS.etStrkeCMYKClr:
        cae OPS.etFllCMYKClr:
        cae OPS.hadngFll:
        cae OPS.etRenderngIntent:
          peratrLt.fnArray.plce(, 1);
          peratrLt.argArray.plce(, 1);
          --;
          cntnue;
        cae OPS.etGState:
          cnt [gStateObj] = peratrLt.argArray[];
          let j = 0,
            jj = gStateObj.length;
          whle (j < jj) {