Assuming the plan isn't too complicated, you could probably get away with one of the following in fairly short time:
1. At one time I remember there is a drafting/art tool that allows you to trace an image on one end and it transfers the image to another paper in a larger size. Sorry, but I don't know what it's called. Unfortunately, quick searches only pull up resizing on computer drawing applications. Sign of the times.
2. If you have access to one, you could use an overhead projector to shine the original plan on a wall, and trace the projection in the size you want.
3. Print a design on 1/4" grid paper. Take a larger sheet of blank paper, and draw a grid on it, dimensioned up to the size you want. Then redraw the design.