Producing scaled objects on new sheet/document sizes

[chrizon]

Hello all, I'm hoping someone can help me to get this right.

So I build model RC planes, I have the plans for a scratch build from depron bought online. The first part of the plan I wish to convert is a PDF (864 × 1118mm). On this plan are panels which I need to cut to from the sheets of depron to produce the model components. 

A friend has a CNC machine which he can use to cut the pieces which will be much cleaner and more accurate than trying to cut by hand. In order to produce these, I need to effectively trace the component outlines from the PDF to smaller (400x 290) sheets, as well as repositioning them so that they can effectively comprise 1 continuous line that can be cut by the machine.

Obviously each of these components need to remain true to scale and size when the new file is produced so that the model comes out in the right proportions and the pieces fit together.

I was imagining that the PDF could be opened and a overlay added in the (400x 290) correct size that would then let me trace/copy the components from the PDF and realign.

Could anyone tell me how to go about this and/or set up the work space in Affinity V1 on Mac?

Any help would be greatly appreciated.

Thanks,

Chris