I never used Premiere Pro as a trial version, but as far as I know the trial version is limited on the export function.
I think you have to buy Premiere.
Thank you for your help. One last question, if I have already downloaded the trial and have put together a video, if I buy the software will I be able to use the video I have created and do all the conversions/exports etc?
Exports have no 'connection' to Adobe software. You can do with them whatever you want.