You are able to set default memos on two levels:
Account-wide (from the Document Settings page in your Account settings section). This applies to all New Projects you create in your account going forward.
Project-wide (from the project creation/edit page - i.e. "Edit Project" - scroll to the bottom and click "Additional Settings", then you can change the defaults). These default memos appear on all documents you create within this project.
**Project memos override account memos, so if you have anything in the project memos it will replace for documents in this project whatever you had saved in the account memos.
Changes to these memos will only appear in new documents or new projects created. If you edit the default memo account-wide but already have an existing project, you will not see these updated memos on that project. You will need to edit the project memos as mentioned above to see these reflected changes.