Hi Liam Robs,

If you want to use custom fonts you will need to add your custom font and the related less/CSS to the web.reports_assets_common assets bundle.

Example:

'assets': {
        'web.report_assets_common': [
           'your_module/static/src/less/fonts.less'
        ],

and let's say this is your fonts.less file

1. web.reports_assets_common

• This speaks about the common resources that Odoo uses for its web-based reports. on Odoo, reports are frequently created and displayed on a web interface. These reports may contain a variety of assets, including JavaScript files, CSS stylesheets, and other resources needed for proper report rendering. 

  2. web.report_assets_pdf

•  This phrase probably has something to do with creating PDF reports in Odoo. With Odoo, you can create PDF versions of many system reports and documents.
• This can contain the materials needed to design the layout, style the PDF output, and guarantee that the content is accurately converted to PDF format.

The main difference is report_assets_common affected on both web view and pdf view while report_assets_pdf does not affected on web view.

Thank you.