What file ext (non pdf) do you use for large plot drawings?

I need to create a large drawing 2 foot x 3 foot (or similar) for a DS Mechanical drawing I've created.  I've exported/saved to a PDF file but when taking it to a place like Staples or similar, they blow up the PDF to a 2 foot x 3 foot and the distortion is so bad you can barely make out the text/numbers. 

It has been recommended that I use an ARCH D output/format but I see nothing like this in RSMechanical when attempting to either save or export. 

Help please!!

Thanks,

CD