Add Scale Bar to Floorplan

I need a scale bar added to an existing floorplan (PDF) that matches the drawing's scale.

Requirements:
- Add a scale bar to the existing floorplan PDF
- Use the width of a room (12 feet / 3.66 meters) as the reference for the scale bar

Ideal skills and experience:
- Proficient in PDF editing
- Experience with architectural or floorplan drawings
- Attention to detail