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):

if (privateUseAreaIndex >= PRIVATE_USE_AREAS.length) {
          warn("Ran out of space in font private use area.");
          break;
        }
        nextAvailableFontCharCode = PRIVATE_USE_AREAS[privateUseAreaIndex][0];
        privateUseOffetEnd = PRIVATE_USE_AREAS[privateUseAreaIndex][1];
      }
      var fontCharCode = nextAvailableFontCharCode++;
      if (glyphId === 0) {
        glyphId = newGlyphZeroId;
      }
      newMap[fontCharCode] = glyphId;
      toFontChar[originalCharCode] = fontCharCode;
    }
    return {
      toFontChar,
      charCodeToGlyphId: newMap,
      nextAvailableFontCharCode,
    };
  }
  function getRanges(glyphs, numGlyphs) {
    
    
    var codes = [];
    for (var charCode in glyphs) {
      
      if (glyphs[charCode] >= numGlyphs) {
        continue;
      }
      codes.push({ fontCharCode: charCode | 0, glyphId: glyphs[charCode] });