If any of your documents are not displayed in English, like for example a Spanish police certificate, you will need to get it translated officially.
The Translation Services http://www.dia.govt.nz/diawebsite.nsf/wpg_URL/Services-Translation-Index

For any copies of your originals (like passport copies or birth certificate copies) your documents will also need to be accredited and the easiest way to do this, if you are already in New Zealand, is to go to the court notary of the city you live in. You will need your passport and they will sign your copies and papers and stamp it. In most cities this service is for free.
Wellington Court notary, 43 - 49 Ballance Street, Lambton Quay, 04 918 4000