You must not change the name of the downloaded report, after having generated it. Should you edit it in any way, HMRC most likely will reject it.

Exception:
If you have generated the report and then downloaded it again, you will potentially have two file with the same name, but (1) at the end of one of them.
If you decide to upload the report with the file name containing the (1) at the end, please make sure to delete only the (1) from the file name before uploading it.