With AutoCAD you have the Modelspace in which you draw in real-time (1:1) so all your dimensions are true. All drawings and annotations are generally done here.

When you print you use the layout tab which helps when setting out pages for different drawings. This is also in real-time so you can set up your pages to the size that you want etc.

A veiwport is what you use to scale your drawing and you can place them in the layout pages:

Click View > Viewports > New Viewports

You can name the viewport, make it to the size you want and have as many as you need on your desired sheet size.

Click on the viewport and a menu should appear in which you can change the scale of that viewport. There are also options to lock the scale as well ( in case you accidentally double click on the view port and zoom).

@recochrane

Thanks Recochrane for the help, that makes life easier.

@Recochrane thanks for that, I never knew about that little tid-bit. I usually double click in the viewport to activate it and then type:

z > enter > scaleXP (1/100XP etc) > enter