Normally, the paper size is set up once—in the environment file—and doesn't need to be changed later. But, occasionally, changing paper size mid-document is needed; for example, to insert a table or a figure in landscape mode. There are two ways to change the paper size mid-document. To illustrate those, let us first define two paper sizes for convenience:
<texcode>\setuppapersizedefinepapersize[main] [A4]\setuppapersizedefinepapersize[extra][A4,landscape]</texcode>
One way to change document size is to permanently change the paper size using <cmd>setuppapersize</cmd> and then revert back using <cmd>setuppapersize</cmd>.