Will I have to pay NI as a freelancer if I am a PAYE employee?

Hello,

I am considering signing myself up a sole trader so I can do some freelance graphic design work for a couple of local business. I will continue to work in full time employment so my question is: will I still have to Pay national insurance as a freelancer when I pay it though my monthly pay checks already?

Sorry if this is a stupid question, Im trying to get my head around this and it's a lot to take in.

Please note, my earnings as a freelancer will not tend to be very heigh. I am aiming for a couple of thousand a year at most. So well within the VAT limits ect...

Thanks for any help!

D