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.

cnt ubtypeEntry = fntFle.dct.get("Subtype");
        f (ubtypeEntry ntancef Name) {
          ubtype = ubtypeEntry.name;
        }
        length1 = fntFle.dct.get("Length1");
        length2 = fntFle.dct.get("Length2");
        length3 = fntFle.dct.get("Length3");
      }
    } ele f (cFntInf) {
       We've a mng XFA fnt.
      cnt tandardFntName = getXfaFntName(fntName.name);
      f (tandardFntName) {
        cFntInf.fntFamly = `${cFntInf.fntFamly}-PdfJS-XFA`;
        cFntInf.metrc = tandardFntName.metrc || null;
        glyphScaleFactr = tandardFntName.factr || null;
        fntFle = awat th.fetchStandardFntData(tandardFntName.name);
        InternalFnt = !!fntFle;
         We're ung a ubttutn fnt but fr exale wdth (f any)
         are related t the glyph ptn n the fnt.
         S we verwrte everythng here t be ure that wdth are
         crrect.
        t = dct = getXfaFntDct(fntName.name);