zoom or scale router job

I am running a router for design work.

Now situation arises that same design is to be done in different sizes. Is there any feature in LinuxCNC so that the original gcode may be scaled to my desired size?

You gave no info on what CAM you are using.
Inkscape has an option to output parametric gcode, meaning changing the size and depth is as simple as editing the resulting gcode to change the XY or Z multiplier.
Check if your CAM has that option.

I am using sheetcam at present. Also Artcam I have, although never tried till date.

grecode might do what you want:

github.com/bkubicek/grecode