You have to update your scenes. If a section plane is visble when you create a scene it will remain visible in that seen even if you hide the section plane. You need to hide it and then update the scene.
Ok, so the I have solved the problem. It appears the problem was intoduced in sketchup 8. All you have to do
is go "file" , "geo-location" , "clear location". For what ever reason that is what is causing the problem. Clear that and
you are good.
First you may wish to read the manual on printing and printing to scale. Secondly. If I want to print a shape that better fits the sheet I change the proportions of my window to the proportions of the page. There's no exact way (I know of) that does this. Thirdly I never print directly from SU anyway. The quality is no good. I export to .png or pdf and adjust the size for the quality I want. At some point I might crop the image again anyway. But now I am beginning to use LayOut a lot for my printing (Pro version only) if I am just outputting a SU picture.
You can type any 'decimal units' as long as you include a units suffix.
So if you are working in inches then typing 18" or 1.5' give the same result.
If you are working in 'mm' but want something that's exactly 18" long you can type 18" and it will be made exactly that long [i.e. 457.2mm] without need to do complex calcs...
Vice versa, if you are working in inches but want something 45cm long then type in 45cm and you'll get something a little less than 18"...