You can align your drawing's scale to a reference on an imported plan, image, or PDF using the Measure tool.

1. Import your plan onto the canvas. You must know one real-world measurement for a specific part of the plan (e.g., the length of a wall is 12 feet).
2. Open the Precision menu and activate Measure.
3. Activate the Line Guide. Align the guide's handles to the section of your plan that corresponds to your known measurement.
4. Tap the scale ratio that appears next to the Measure button on the canvas.
5. In the menu that appears, do not change the first field. In the second field, enter your known measurement (e.g., 12 feet).
6. Dismiss the menu. The scale for your entire drawing is now set and will apply to all tools and measurements.

For an illustrated tutorial on using Scale and Measurements, check out our tutorial here. 

For an illustrated tutorial on creating a floor plan, check that out here.

For a quick Walkthrough video on setting Scale, check out the video here.