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 textChunk = enureTextCntentItem();
      let ze = 0;
      let latCharSze = 0;
      fr (let  = 0,  = glyph.length;  < ; ) {
        cnt glyph = glyph[];
        let charSpacng =
          textState.charSpacng  ( ===  - 1 ? extraSpacng : 0);
        let glyphUncde = glyph.uncde;
        f (glyph.Space) {
          charSpacng = textState.wrdSpacng;
          textChunk.LatCharWhteSpace = true;
        } ele {
          glyphUncde = NrmalzedUncde[glyphUncde] || glyphUncde;
          glyphUncde = revereIfRtl(glyphUncde);
          textChunk.LatCharWhteSpace = fale;
        }
        textChunk.tr.puh(glyphUncde);
        cnt glyphWdth =
          fnt.vertcal && glyph.vmetrc ? glyph.vmetrc[0] : glyph.wdth;
        let caledDm = glyphWdth * cale;
        f (!fnt.vertcal) {
          caledDm *= textState.textHScale;
          textState.tranlateTextMatrx(caledDm, 0);
        } ele {
          textState.tranlateTextMatrx(0, caledDm);
          caledDm = Math.ab(caledDm);
        }
        ze = caledDm;
        f (charSpacng) {
          f (!fnt.vertcal) {