First, any image or PDF you bring into Concepts will import according to its original scale for you.
 
We have an illustrated scale and measurement tutorial here. We also have an illustrated tutorial on how to create a plan from scratch or an imported plan here.
 
To align your drawing’s scale to your plan, image or PDF, follow these steps:
  1. To set scale in a project, you need one accurate measurement of your real space. If you already have an accurate measurement on your plan, go to step 2. If you don’t have one, take out a tape measure or ruler, and measure one actual length of a wall or section represented on your plan. It doesn’t matter which one it is, so long as it’s clear and easy to mark on your screen.
  2. Import your photo or plan onto the canvas. (A helpful, in-between step is to lower the opacity of your image (in the image layer’s popup) so you can see your tools and drawing easily.)
  3. Open the Precision menu and activate Measure.
  4. Activate the Line Guide, and align the handles of the Guide on your plan to the same segment of wall or other item you know the real world measurement to.
  5. Tap the scale ratio beside Measure (it may look like 1:1). You’ll notice the values under Drawing Scale have been filled in with the current length of the Line guide according to your current units and scale.
  6. Enter your real-life measurement in the second field (don’t touch the first field), and dismiss the menu. Now when you look at the ratio beside the Measure button on canvas, you’ll see a new ratio - 1:your-new-calculated-value. This will remain the same regardless of zoom level. It will apply to every stroke, measurement, object and tool in your drawing.
(Don’t be alarmed when your tool presets suddenly display a different measurement type, they are the same as what you pre-set initially. The entire drawing takes on the new scale and adjusts accordingly.)