Imagine self-signed certificate used for zabbix frontend. Or when cert is expired.
In such case generated report is just blank.

There is workaround if web_service is running locally it would be possible to add "--allow-insecure-localhost" command line option to "chrome" which allows to still generate such reports.
I think it would be useful to add this option to source code.

As for external sites - I'm not sure. We probably will document that as a know limitation.
Or maybe there is a way to add self-signed to system level certs storage?

Also, errors handling probably could be improved, if possible, because it's not clear at all why generated PFD is blank.