Autocad scale command
It might take a little getting used to at first, but you draw everything in Autocad software at one to one, in units of your choice. So for example a 5 mtr wall is drawn as line of 5000 units, each unit being 1 mm.
In most industries one unit will be taken as 1 mm. So when you come to scale your drawing you will be able to set a viewport to a scale of 1:50. Windows will measure the paper size in mm's and a 1:50 scale drawing will be plotted.
However the viewport scale would have to be adjusted if you have used 1 unit = 1 mtr.
So to get 1:50 plot when you have used metres, turn your 1:50 into a decimal. That's 1/50 = 0.02.
Then multiply this value by 1000 to give you 20. So your viewport scale should be 20:1 to ptoduce a scale of 1:50. In all scaling you must do check measurements on known distances to ensure that your plot is correct.
Indeed it's sometimes easier to use the scale command on your metre drawing and scale up to mm's.
The scale command works by through the selecting objects routine, then after you have pushed enter to finish selecting objects, will ask you for a base point.
This is the point about which the X and Y scales will be adjusted.
Then you will be asked to supply a scale factor.
Think of a simple line of 5 units which needs to be scaled up to 10. You can probably see that the scale factor is 2. However that's worked out by 10/5.
So if you have a line which is 1200 and it needs to be scaled up to 1600, then the scale factor will be 1600/1200.
To scale down down from 1200 to 800 the scale factor would be 800/1200