Are you already using the dimension style settings ( DDIM ) ?

Many thanks

kc

Are you going to draw in inches / feet or mm / meters ?

Are you going to use Iso paper sizes or Imperial paper sizes ?

A4 is 210 mm x 297 mm but if you print in the UK it would rather be an imperial format like 8.5 " ( 215.9 mm ) x 11 " ( 279.4 mm ) if I remember well.

I have an example of each that is based on a double rectangle.

The outside rectangle is the exact format and the inner rectangle is a copy/scale of the outter with a factor that prints at scale 1/1 on a small printer that has margins that would spoil the scale if printed on the outter rectangle.

For the rest the formats A4 to A0 and the imperial ones named also A , B , C , etc... should be involved into a "prototype" file of yours including all the AutoCAD blocks usefull to begin a drawing such as all the layers, dimension styles, tittle blocks, notes, etc...

In addition I would say that your "prototype" should have settings different if metric or imperial such as the UNITS, text height 2.5 mm ( metric ) or 0.2 " ( imperial ), settings of the centerlines and hidden lines, etc...

When starting a new drawing from no "prototype" you have eventually to choose iso or imperial if I remember well.