Please ask the director/cosplay staff at the convention where this particular Hall Cosplay Contest is being held, because every one of them is run differently, and while some may want you to bring stuff, others are not judged so strictly, and others may still judge but won't bother looking at your documentation. We here on a forum can't say what they'll want, only the staff at THAT CON will be able to tell you what they would like you to bring in terms of documentation.
After all, I only attend cons where "hall cosplay contest" is someone walking up to you in the hallway, telling you "you look fantastic," and handing you a ribbon or a button. No reference, no documentation, no judging, just a sneaky expert costumer with a good eye for pretties. But that's...those cons. No two cons do it exactly the same. Ask the con first. Always ask the con staff first.
Founder and President, Madison Area Costuming Society, a chapter of the International Costumer's Guild
Strange Land Costuming - www.strangelandcostumes.com