In this video we are solving a community question. They have created a flow that sends an email and now they need to add the attachment from the task that triggered the flow to the mail being sent. You can find the question here: ...
Assuming the attachment is already saved in the system, you can just add a record in the sys_attachment table, put sc_task for table, the catalog task' sys_id as table sys_id and then copy the rest of the fields from the original attachment...
Your biggest problem will likely be to ensure that you have a good copy of the attachment and how to manage the inevitable updates that will come to it later on...
That being said as a quick and dirty solution to the question asked. You may want to challenge the use of a fixed attachment. If it is to capture data, that should be done in SN directly instead of storing that in a PDF, if it is to provide fixed data, like a how-to, a KB should suffice.
