Install wkhtmltopdf in ubntu/odoo

1. Download wkhtmltopdf package from here.
2. Install it by using below command.

dpkg -i wkhtmltox-0.12.2.1_linux-trusty-amd64.deb

          [Note : Some times it gives dependency error for other package like   
           xfonts-75dpi, to solve that follow below steps.]

                 1. sudo apt-get update
                 2. sudo apt-get -f install

3. Copy link to usr/bin folder using below commands

 sudo cp /usr/local/bin/wkhtmltopdf /usr/bin
 sudo cp /usr/local/bin/wkhtmltoimage /usr/bin

4. Now Change odoo system parameter(Settings->System Parameter)
Create new parameter if not exist with name webkit_path and set value
/usr/bin/wkhtmltopdf