Generated PDF uses some strange font sets which make the PDF unreadable. It's very rare, might be related to that one specific article. I didn't reproduce this error on different articles, but I also didn't try too much.
Article: https://en.wikipedia.org/wiki/Mahatma_Gandhi
Chromium render url: http://chromium-pdf.wmflabs.org/en.wikipedia.org/v1/pdf/Mahatma_Gandhi/letter
{F11771324}
{F11771323}
PDFFonts output shows different font sets used in both files.
```
raynor@DellE6540:~/TODO/broken_renders » pdffonts d_broken_fonts.pdf
name type encoding emb sub uni object ID
------------------------------------ ----------------- ---------------- --- --- --- ---------
DejaVuSans-Bold CID TrueType Identity-H yes no yes 52 0
LiberationSans-Bold CID TrueType Identity-H yes no yes 57 0
DejaVuSans CID TrueType Identity-H yes no yes 62 0
LiberationSans CID TrueType Identity-H yes no yes 67 0
DejaVuSerif-Bold CID TrueType Identity-H yes no yes 72 0
LiberationSerif-Bold CID TrueType Identity-H yes no yes 77 0
LiberationSerif CID TrueType Identity-H yes no yes 82 0
DejaVuSerif CID TrueType Identity-H yes no yes 87 0
LiberationSerif-Italic CID TrueType Identity-H yes no yes 95 0
LiberationSans-Italic CID TrueType Identity-H yes no yes 107 0
LiberationSerif-BoldItalic CID TrueType Identity-H yes no yes 120 0
LiberationSans-BoldItalic CID TrueType Identity-H yes no yes 132 0
raynor@DellE6540:~/TODO/broken_renders » pdffonts d_correct.pdf
name type encoding emb sub uni object ID
------------------------------------ ----------------- ---------------- --- --- --- ---------
LiberationSans CID TrueType Identity-H yes no yes 125 0
LiberationSans-Bold CID TrueType Identity-H yes no yes 130 0
DejaVuSans CID TrueType Identity-H yes no yes 135 0
LiberationSerif-Italic CID TrueType Identity-H yes no yes 140 0
LiberationSerif CID TrueType Identity-H yes no yes 145 0
LiberationSerif-Bold CID TrueType Identity-H yes no yes 150 0
DejaVuSans CID TrueType Identity-H yes no yes 155 0
LiberationSans-BoldItalic CID TrueType Identity-H yes no yes 173 0
DejaVuSerif CID TrueType Identity-H yes no yes 182 0
LiberationSans-Italic CID TrueType Identity-H yes no yes 202 0
```