No designer I know would allow that. Almost everyone directs that their drawings are invalid if scaled. It also violated copyrights, which is the least of the issues. Kevin points out things like doors and windows that wouldn't make sense. Other things include hallways that would become larger than necessary, walls that would be the wrong size, kitchens that don't match the cabinetry, spacing between receptacles that don't measure up to code, and so on. A 4" wall thickness would measure to 5", for example. Would you buy 2x5's (?) or just tell the builder to adjust?
When I draw plans, whenever possible, I try to design in efficient increments, so that full sheets of plywood, or full tiles, or whatever can be used. The houses I design using ICF's in conjunction with air formed roofs are dimensioned, whenever possible, to use whole blocks, because cuts add labor. Scaling the drawing screws up any of the designer's intentional planning.
The proper way to handle this is to talk to the original designer and tell them you want that plan but larger, and they'll need to talk you through the cost and design implications of doing so.