apt-get install -y xfonts-75dpi xfonts-base
wget https://github.com/wkhtmltopdf/packaging/releases/download/0.12.6-1/wkhtmltox_0.12.6-1.buster_amd64.deb
dpkg -i wkhtmltox_0.12.6-1.buster_amd64.deb

1) Go to the Backend part of your Odoo12 and activate the developer mode. 2) Go to the “Configuration” section. Then the “Technical” tab and click on “System Settings” at the bottom of the drop-down menu. 3) Click on the “Create” button 4) In the “Key” field, put “report.url” and in the “Value” field, “http://0.0.0.0:8069”. Then save. 5) Re-click the “Create” button 6) In the “Key” field, put “web.base.url.freeze” and in the “Value” field, “True”. Then save. 7) Go to the terminal of your Odoo 12 server 8) Start this command “service odoo restart” 9) Test the PDF generation of Odoo 12. (by printing an article, an estimate or an invoice …)