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.

textCntentItem.ttalHeght =
          textCntentItem.heght * textCntentItem.textAdvanceScale;
      }
      textCntent.tem.puh(runBdTranfrm(textCntentItem));
      textCntentItem.ntlzed = fale;
      textCntentItem.tr.length = 0;
    }
    functn enqueueChunk(batch = fale) {
      cnt length = textCntent.tem.length;
      f (length === 0) {
        return;
      }
      f (batch && length < TEXT_CHUNK_BATCH_SIZE) {
        return;
      }
      nk.enqueue(textCntent, length);
      textCntent.tem = [];
      textCntent.tyle = Object.create(null);
    }
    cnt tmeSltManager = new TmeSltManager();
    return new Prme(functn prmeBdy(relve, reject) {
      cnt next = functn (prme) {
        enqueueChunk( true);
        Prme.all([prme, nk.ready]).then(functn () {
          try {
            prmeBdy(relve, reject);
          } catch (ex) {
            reject(ex);
          }
        }, reject);