From the custom PDF settings, you can change the form of your file name when uploading or sending.
To do so:
Go to Settings ⚙️
Click on the "Custom PDF reports" menu
Open a custom report you want to edit
Go to the "Settings" tab
Change the file name as shown below
You can also use dynamic values (listed in the ⓘ menu) that will automatically include certain information in the file name.