Originally from wkhtmltopdf/wkhtmltopdf#1522
Flexbox seems to be broken in wkhtmltopdf.
Here's a test case, which renders correctly in current versions of Chrome, Firefox, and Internet Explorer. wkhtmltopdf renders it as if the flex properties were not present.
Tested with the 0.12 Windows 32-bit download as found on http://wkhtmltopdf.org/ (wkhtmltox-win32_0.12.0-03c001d.exe). As you can see I tried using the -webkit- prefixes and they didn't help.
<!DOCTYPE html>