child theme font size change not taking effect

I used the instructions below to create an area in my child theme so that I can modify the font size on the packing slip:

“Want to use your own template? Copy all the files from wp-content/plugins/woocommerce-pdf-invoices-packing-slips/templates/Simple to your (child) theme in wp-content/themes/storefront child/woocommerce/pdf/yourtemplate to customize them”

Then I went into the style.css of my child theme (in the pdf folder noted above) and changed the font size from 9pt to 12pt. The packing slip looks the same. What am I doing wrong, or what else do I need to do?

The page I need help with: [log in to see the link]