I want to store the transaction using a specific PDF template on create and each time the record is amended. The file should store under the communications tab of that record and a new PDF each time the record is amended... is this possible and how can I do this? Prefixing the pdf doc with todays date would be ideal...

This is possible, it will require a UserEvent script. The script can, on save essentially, generate a new PDF file, save it to the file cabinet, then associate the file to the transaction record. You can make the name of the PDF almost anything you want that is valid as a file name.

@G if you use workflows you can do this with a custom action as well. This company made an action you can download that will create a pdf of a record https://www.mgbcpro.com/enhanced-workflow-actions