Hello,

this is the problem of  Wkhtmltopdf:
Please refer this link :  http://parikshitvaghasiya.blogspot.in/2015/08/how-to-install-proper-wkhtmltopdf-for.html

Hope this will help you!!

Yes, I am also for long time have same issue and not yet solved for me, but there is a solution which I didn't try yet that the Wkhtmltopdf versions 0.12.2 and 0.12.2.1 are seems to have some regressions: --dpi ignored and javascript links not processed and you should use wkhtmltopdf 0.12.1