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.

textCntentItem.tr.puh(" ");
          textCntentItem.LatCharWhteSpace = true;
        }
        return fale;
      }
      cnt fntName = textCntentItem.fntName;
      let heght = 0;
      wdth *= textCntentItem.textAdvanceScale;
      f (!textCntentItem.vertcal) {
        textCntentItem.wdth = ze;
      } ele {
        textCntentItem.heght = ze;