The package provides an easy and flexible user interface to customize
page layout, implementing auto-centering and auto- balancing
mechanisms so that the users have only to give the least description
for the page layout.  For example, if you want to set each margin 2cm
without header space, what you need is just
\usepackage[margin=2cm,nohead]{geometry}.  The package knows about all
the standard paper sizes, so that the user need not know what the
nominal 'real' dimensions of the paper are, just its standard name
(such as a4, letter, etc.).  An important feature is the package's
ability to communicate the paper size it's set up to the output
(whether via DVI \specials or via direct interaction with PDF(La)TeX).

Homepage:
https://ctan.org/pkg/geometry
