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.

font = new Stream(new Uint8Array(font.getBytes()));
    let header, tables;
    if (isTrueTypeCollectionFile(font)) {
      const ttcData = readTrueTypeCollectionData(font, this.name);
      header = ttcData.header;
      tables = ttcData.tables;
    } else {
      header = readOpenTypeHeader(font);
      tables = readTables(font, header.numTables);
    }
    let cff, cffFile;
    const isTrueType = !tables["CFF "];
    if (!isTrueType) {
      const isComposite =
        properties.composite &&
        ((properties.cidToGidMap || []).length > 0 ||
          !(properties.cMap instanceof IdentityCMap));
      
      if (
        (header.version === "OTTO" && !isComposite) ||
        !tables.head ||
        !tables.hhea ||
        !tables.maxp ||
        !tables.post
      ) {
        
        cffFile = new Stream(tables["CFF "].data);
        cff = new CFFFont(cffFile, properties);
        adjustWidths(properties);
        return this.convert(name, cff, properties);