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):

num.set(this.buffer.subarray(this.pos, this.pos + size + 1));
      this.pos += size + 1;
    },
    readHexNumber(num, size) {
      var last;
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        sp = 0;
      do {
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        if (b < 0) {
          throw new FormatError("unexpected EOF in bcmap");
        }
        last = !(b & 0x80);
        stack[sp++] = b & 0x7f;
      } while (!last);
      var i = size,
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        while (bufferSize < 8 && stack.length > 0) {
          buffer = (stack[--sp] << bufferSize) | buffer;
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        num[i] = buffer & 255;
        i--;
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      }
    },
    readHexSigned(num, size) {