If you would like a different file name for a PDF then you can change the PDF Filename by going into Web Portal > Forms > View Form Templates > three dots to the right of the screen > Actions.

In the Actions, you can edit email action > scroll to PDF Filename. You can type in what you would like the PDF File name to be. You can also add in the Placeholders (responses from the form content will be populated) by using Ctrl + Space, and selecting the objectname of the field that you would like to appear from the dropdown list.