Adding images to Document Template

Hi,

I’m trying to create a receipt similar to the template however I want to add an image. Is there a way to upload an image to use in the template instead of using an external URL ?

This image would be the same for all events so I don’t want to have to upload the image to all events created either.

It could also be a “private” image such as a signature so I want to keep this restricted, not publicly available as an event material either.

Is there anything I can do ?

I am using v3.3.2 and I am an admin

Many thanks