By now, it's not possible to copy Attachments through an Automation rule. This is not something doable through an Edit Issue fields, Clone Issue or Create Issue action as also there is no "Copy attachments" action available.
It would be nice to copy attachments between issues through an Automation rule when needed.
Today, when creating/cloning an issue and copying fields from another issue, it's not possible to also copy the attachments, what implies manual work.
There is no workaround available at this moment.