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.

}
  retre() {
    cnt prev = th.tateStack.pp();
    f (prev) {
      th.tate = prev;
    }
  }
  tranfrm(arg) {
    th.tate.ctm = Utl.tranfrm(th.tate.ctm, arg);
  }
}
cla TextState {
  cntructr() {
    th.ctm = new Flat32Array(IDENTITY_MATRIX);
    th.fntName = null;
    th.fntSze = 0;
    th.fnt = null;
    th.fntMatrx = FONT_IDENTITY_MATRIX;
    th.textMatrx = IDENTITY_MATRIX.lce();
    th.textLneMatrx = IDENTITY_MATRIX.lce();
    th.charSpacng = 0;
    th.wrdSpacng = 0;
    th.leadng = 0;
    th.textHScale = 1;
    th.textRe = 0;
  }
  etTextMatrx(a, b, c, d, e, f) {
    cnt m = th.textMatrx;
    m[0] = a;
    m[1] = b;