Download correct version for internet
wget -P Downloads http://download.gna.org/wkhtmltopdf/0.12/0.12.1/wkhtmltox-0.12.1_linux-trusty-amd64.deb
Install debian package
dpkg -i wkhtmltox-0.12.1_linux-trusty-amd64.deb
Move to installation path
cd /usr/local/bin
Link the created files
ln -s /usr/local/bin/wkhtmltoimage /usr/bin/wkhtmltoimage
ln -s /usr/local/bin/wkhtmltopdf /usr/bin/wkhtmltopdf
Or copy the created files
cp wkhtmltoimage /usr/bin/wkhtmltoimage
cp wkhtmltopdf /usr/bin/wkhtmltopdf