I am really struggling to understand how to easily edit a SketchUp model, or in my personal case a floor plan, in Layout. All I want to do is change each line width, as I need some heavier than others in the plan, and size it to scale 1:25. I can figure the scale, but I can’t seem to easily edit the plan, and when I try to do this I lose the scale. It’s driving me just slightly mad to say the least. It looks easy on YouTube but it’s not working for me sadly. Simply understanding how to edit the SketchUp model in Layout it would help 
Thank you!
In order to change individual line widths of the floorplan, you would need to first render the viewport as Vector or Hybrid. Then explode it so the lines become LayOut entities. You may need to ungroup the lines and you may need to split some of them using the Split tool (knife blade tool on toolbar). Then you can select the lines and change their weight in Shape Style in the tray.
There are better ways to do it which don’t require exploding the viewport and breaking the link to the SketchUp model, though. They would require some additional scenes in SketchUp, proper layer usage in both SketchUp and LayOut, and stacking viewports in LayOut.
As for scaling the viewport, Make sure that in Sketchup, the camera for the scene is set to Parallel Projection and you’ve set the standard Top view. Then the viewport can be set your chosen scale in the SketchUp model inspector panel in LayOut or in the context menu when you right click on the viewport.
Thank you DaveR, I’ll give this a go now. When I was experimenting I did somehow (although no idea how) manage to edit the lines having exploded the model, but then I didn’t know how to then come out of this. Would I then need to group?
Thanks for your help.
It won’t hurt to group sets of lines.
Getting out of editing can be done with Each or just clicking out away from the drawing.