How to add a new button and a new screen to a standard transaction

Hi.

I need to add a new button bar and a new screen to VF03 transaction. The new button function is to display a PDF document that is out of SAP. I already have the functionality that opens and display the PDF document ant it uses a screen, but now I need to add it at VF03 standard transaction.

I don’t have really clear if I could do it with a menu exit or if I have to make a standard modification.

Can anybody help me or give me any ideas?

Thanks.

Diana.