Most likely, such things are done in the driver, not in the printer. So you ask the manufacturer. That would even be the advice if it is done in the printer, since not all printers are created equal.
Asking the sales person in the shop for a demo would be fine also. Just take such a pdf with you on a USB-stick and see how it prints from their PC (assuming your POS-server runs Windows).
I'm setting up a pos system for my retail store and I already found a software that allows me to manage inventory and transactions. Unfortunately, the receipts are not customizable and the use up an entire pdf page. Before I purchase a printer for receipts, I'd like to know if thermal printers will scale the page down to the size of the paper. It doesn't have to be pretty, just show the details of the transaction.