How did you export to the PDF? What settings did you use? If you used the view as it shows in the SKP file, you missed setting the camera to Parallel Projection, setting the standard Top view, and setting the window size so the panel fills the frame. You probably also missed setting the option for Full Scale. Without setting the Camera to Parallel Projection, scale doesn’t make any sense and so it wouldn’t be something you could set anyway.
Notice that when your PDF is setup to print at 100% using Adobe Reader’s poster option, yours would print out the panel very large. So if you told the people at Fed Ex to print it on a sheet that would contain the correctly sized drawing, it would print out too small.
I set the Camera to Parallel Projection, standard Top View and I shortened the height of the model window to more closely approximate the shape of the panel. Then I set up the PDF as shown above and I got this. It appears to be much more appropriate for the size of the panel.
With all that said, setting something like this up to print at full size is much more easily and dependably achieved in LayOut although you’d need to be using SketchUp Pro to have LayOut.