Plt Document Size

Dear E3D Master,

I need to know how to generating PLT file, with specific size. 

as far i know, here my step.

1. Open Draw (in BACK type drawing, not SHEE)

2. Import the AutoCAD

3. Export to PLT

But the problem is, i can get the square size while exported to plt.

the result is strict to paper size as below :

the result is, 

DETAIL 1. I'm generating from step above, with size ISO A8 (closed to size that i required, which is 49x49)

DETAIL 2. I'm getting this plt from default aveva. 

So in need to know, how to generate plt with size 49x49?

Thank's