You can add existing model or file documents to your project using the Toolbox, Browser, or drag and drop.
Click the Add Project Document tool in the Toolbox, click in the diagram to open a standard Open dialog box, browse to and select one or more documents in your file system, and then click Open.
Drag and drop one or more documents from:
The file system to the Browser or to the project diagram. If a folder has sub-folders, the hierarchy is preserved when it is added to the project. However, since projects are not synchronized with the file system, if you subsequently add files to these folders outside PowerDesigner, they will not automatically be displayed in the Browser.
A project diagram to another project diagram.
The Browser to the project diagram.