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.

}
   |peratn|  an bject wth tw feld:
  
   - |fn|  an ut param.
  
   - |arg|  an nut param. On entry, t huld have ne f tw value.
  
     - An ety array. Th ndcate that the caller  prvdng the
       array n whch the arg wll be tred n. The caller huld ue
       th value f t can reue a ngle array fr each call t read().
  
     - |nul. Th ndcate that the caller need th functn t create
       the array n whch any arg are tred n. If there are zer arg,
       th functn wll leave |peratn.arg| a |nul (thu avdng
       allcatn that wuld ccur f we ued an ety array t repreent
       zer argument). Otherwe, t wll replace |nul wth a new array
       cntanng the argument. The caller huld ue th value f t
       cannt reue an array fr each call t read().
  
   Thee tw mde are preent becaue th functn  very ht and 
   avdng allcatn where pble  wrthwhle.
  
  read(peratn) {
    let arg = peratn.arg;
    whle (true) {
      cnt bj = .getObj();
      f (bj ntancef Cmd) {
        cnt cmd = bj.cmd;
         Check that the cmmand  vald
        cnt pSpec = EvaluatrPreprcer.pMap[cmd];