This is referencing a Drupal 7 website with CiviCRM 5.36.x
When CiviCRM prints from a modal it invokes print.css which lives in /sites/all/modules/civicrm/css/. It does not invoke any other theme level css or the custom css that can be set in Administer/System Settings/Resource URLs.
In the case I'm working on, I have attached custom fieldsets to my membership types and applicants can apply via a webform to include a great deal of data.
If I view a membership from a contact record and print, the OEM print.css is invoked and the printed result or PDF is useless. To overcome this shortcoming, I've modified print.css but I'm looking for a long-term sustainable solution.
How does one override print.css with custom css?