I have relocated my Odoo v11 CE from AWS Ubuntu 16.04 to Digital Ocean 18.04. All of the reports have a larger font on the new server (18.04): Invoices, Sales Orders, financial reports (both built-in Odoo and OCA), WH-IN and WH-OUT documents, etc. all have a bigger font size than on the old server (16.04) (in the report header, footer, and body).

The same version of wkhtmltopdf is installed on both servers: 

wkhtmltopdf 0.12.5 (with patched qt)

Does anyone know how to fix this? Is there a default font size for Ubuntu that Odoo reads and uses? There's too many reports to fix manually.