Visualize the limits of the A4 page of the drawing

When I choose a page size in "Drawing Preferences", for example A4, the page boundaries are not displayed anywhere on the drawing area.
What should I do to visualize the limits?

In drawing (normal) mode the paper size is not shown. You have to draw a box yourself, you may safe it as a template for repeated use. If your drawing is intended for scale 1:1 and your units are mm, it's easy, the box has to be 297x210 mm. If your scale is 1:100, it has to be 100 times larger. If the units are cm, m, or even inch, it gets more complicated, can be confusing.
In Print Preview mode the paper sheet is displayed, you have to set the intended scale and move the drawing to the right place, if the drawing border and the paper size both are A4, you can just center it.