You can export to a former version following these steps:

1. Deactivate your project.
2. Select File–> Export–> Data (*.pfd, *.dz) from the main menu and select the project to export.
3. Select the file location where you want to save your file.
4. The export dialog will be shown. Enable the option 'Export to former PowerFactory version'.
5. Select the PowerFactory version to which you want to export.