Attach (recommended) or Link to PDF file here:
https://www.nta.go.jp/taxes/tetsuzuki/shinsei/annai/joyaku/annai/pdf2/250.pdf

Configuration:
- Web browser and its version: Firefox 81.0a1
- Operating system and its version: Debian 5.6.7-1
- PDF.js version: latest in Firefox nightly
- Is a browser extension: No

Steps to reproduce the problem:
1. Open the pdf and paste the following text "本 店 又 は 主 た る 事 務 所 の 所 在 地" in "Full name" and in "Domicile and residence" textfields
2. Print or Save the pdf 

What is the expected behavior? (add screenshot)
![image](https://user-images.githubusercontent.com/5641725/91207547-30f05480-e709-11ea-9abd-2af5d970dc46.png)

What went wrong? (add screenshot)
![image](https://user-images.githubusercontent.com/5641725/91207663-69902e00-e709-11ea-8a1d-1ddd30cf0621.png)

Link to a viewer (if hosted on a site other than mozilla.github.io/pdf.js or as Firefox/Chrome extension):

this.readHexNumber(num, size);
      var sign = num[size] & 1 ? 255 : 0;
      var c = 0;
      for (var i = 0; i <= size; i++) {
        c = ((c & 1) << 8) | num[i];
        num[i] = (c >> 1) ^ sign;
      }
    },
    readString() {
      var len = this.readNumber();
      var s = "";
      for (var i = 0; i < len; i++) {
        s += String.fromCharCode(this.readNumber());
      }
      return s;
    },
  };
  function processBinaryCMap(data, cMap, extend) {