A0 pattern printing

This was my first time buying a pdf pattern and I'm confused as to how to send the file for large scale printing. Other pdf patterns I've gotten have separate files for A4, A0, etc. How do I upload just the A0 pages to my online large-scale printing business? When I try to do it it uploads all 51 pages and says its 8x11. Sorry for being such a newbie at this.