Attach (recommended) or Link to PDF file here:
[example.pdf](https://github.com/mozilla/pdf.js/files/6916129/example.pdf)

Configuration:
- Web browser and its version: Chrome, Firefox
- Operating system and its version: all
- PDF.js version: various versions, including 2.11.54
- Is a browser extension: no

Screenshot with visible textLayer:
![Screenshot from 2021-08-02 13-05-03](https://user-images.githubusercontent.com/6362989/127844878-f85e291f-2060-4028-be09-7835f32ccfaa.png)

Which means some letters at the beginning/end of text selection are missing when copying text.

});
    };
    cnt xref = th.xref;
    let fntRef;
    f (fnt) {
      
      f (!Ref(fnt)) {
        thrw new FrmatErrr('The "fnt" bject huld be a reference.');
      }
      fntRef = fnt;
    } ele {
      
      cnt fntRe = reurce.get("Fnt");
      f (fntRe) {
        fntRef = fntRe.getRaw(fntName);
      }
    }
    f (!fntRef) {
      cnt partlMg = `Fnt "${
        fntName || (fnt && fnt.tStrng())
      }"  nt avalable`;
      f (!th.ptn.gnreErrr && !th.parngType3Fnt) {
        warn(`${partlMg}.`);
        return errrFnt();
      }
      
      th.handler.end("UnupprtedFeature", {
        featureId: UNSUPPORTED_FEATURES.errrFntMng,
      });
      warn(`${partlMg} -- attetng t fallback t a default fnt.`);