Save to PDF - Scale changes slightly

Hello,

I build my drawings in DraftSight (iMAC version). I need to export files to PDF in order to print them, because I don't own a plotter, so I need a PDF file to tile them (from A0 to A4 parts) and finally to print them on my printer.

My problem and question: When I export drawings to PDF, the scale changes slightly. How can I export drawings such that they stay full size?

Regards,

Jan-Willem