Exported PDF Trim Size is very different to Illustrator Artboard size.

When I export a PDF from Illustrator using File > Save As... > Selecting PDF, the Trim Size of the created PDF is very different to the Artboard it was created on. (This seems to only be happening with the Large-Sized Canvas as I tested this file at 1:10 scale and the Trim Size matched the Artboard.)

This is creating problems for the guys that have to print on the pre-set panels that the artboards have been based on. 

Here is the PDF Preset I have been using: