Using Existing PeopleSoft Documents in Layouts
You can link an existing PeopleSoft document to a layout.
However, if a document is used by other metadata in the system, there is a chance that you will not be able to modify the document. For example, if a document is write-restricted or in used by a message in the runtime tables, you cannot modify the document.
If you think you will need to modify a document the best course of action is to make a copy of the document and then write-restrict the document in the Mobile Application Platform component or in the Documents component.