You need to:
1: Create a European PSN account and username
2: Import a European PSN Network money card thingy...I don't know what it's called officially. You can buy these on Ebay and they'll email the validation code so you can use your funds immediately.
3: Use said funds to pay for your Downloadable content. You'll only be able to use the DLC on your European account name.

P.S. This works with your North American Pulse version/PSP. The account/username is what matters.