exporting to pdf and loosing part of file

Hi all,

I have a large banner design I have made up in IndesignCC, it measures 5400mmx800mm

When I export the file as a PDF, it appears to crop the file down width wise, almost like acrobat is slightly zoomed in, just one side is missing, and looks like it approximately has cut off 400mm?

I tried exporting as a JPEG and the whole banner is displayed perfectly? What am I missing?

Thanks in advance

Zac