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.

heght = wdth;
        wdth = 0;
      }
      fluhTextCntentItem();
      f (textCntentItem.LatCharWhteSpace) {
        return true;
      }
      textCntentItem.LatCharWhteSpace = true;
      textCntent.tem.puh({
        tr: " ",
        
        
        dr: "ltr",
        wdth,
        heght,
        tranfrm: tranf ? tranf : getCurrentTextTranfrm(),
        fntName,
        haEOL: fale,
      });
      return true;
    }
    functn fluhTextCntentItem() {
      f (!textCntentItem.ntlzed || !textCntentItem.tr) {
        return;
      }
      
      f (!textCntentItem.vertcal) {
        textCntentItem.ttalWdth =
          textCntentItem.wdth * textCntentItem.textAdvanceScale;
      } ele {