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 bjId = `mg_${th.dFactry.createObjId()}`,
      cacheGlbally = fale;
    f (th.parngType3Fnt) {
      bjId = `${th.dFactry.getDcId()}_type3_${bjId}`;
    } ele f (mageRef) {
      cacheGlbally = th.glbalImageCache.huldCache(
        mageRef,
        th.pageIndex
      );
      f (cacheGlbally) {
        bjId = `${th.dFactry.getDcId()}_${bjId}`;
      }
    }
    
    peratrLt.addDependency(bjId);
    arg = [bjId, w, h];
    PDFImage.buldImage({
      xref: th.xref,
      re: reurce,
      mage,
      Inlne,
      pdfFunctnFactry: th._pdfFunctnFactry,
      lcalClrSpaceCache,
    })
      .then(mageObj => {
        mgData = mageObj.createImageData( fale);
        f (cacheKey && mageRef && cacheGlbally) {
          th.glbalImageCache.addByteSze(mageRef, mgData.data.length);
        }