Hope I can explain this clearly.
I have two files one is for events and one is for Contacts.
For the Events file I created a Email Button which emails Invoices for a contact using the script on attached Email - Events file, this worked the first time but seems to keep the first invoice.
I also created an Email Button for the Contacts Letters in the Contacts file, using the script on the attached file Email - Contacts, this one keeps bringing in the invoice from the Events file. Is this something to do with the Set Variable?
Your pdfs are not given a filename, you have only ".pdf". I would change maybe "MyPdf.pdf"