You can edit the file name of PDF/Word files that you have uploaded/forwarded into Step 3:Documents of a trip itinerary.
1. Proceed to Step 3:Documents of the trip itinerary and select the Edit button next to the attached file
Below, the PDF file that has been uploaded is named 'HotelConfirmation_5483763458'
2. Type in the new file name and click Save
Below, we can see that we have re-named the PDF file: GrandHyattConfirmation