<fo:layout-master-set>
<fo:simple-page-master
master-name="simple"
page-width="210mm"
page-height="297mm">
<fo:region-body/>
</fo:simple-page-master>
</fo:layout-master-set>
[Source]<fo:layout-master-set>
<fo:simple-page-master
master-name="simple"
page-width="210mm"
page-height="297mm">
<fo:region-body column-count="2" />
</fo:simple-page-master>
</fo:layout-master-set>
In the content if you want for example a title to span both columns you have to include it in a fo block with the attribute span="all".

<fo:layout-master-set>
<fo:simple-page-master master-name="simple"
page-height="29.7cm"
page-width="21cm"
margin-top="1cm"
margin-bottom="2cm"
margin-left="2.5cm"
margin-right="2.5cm">
</fo:simple-page-master>
</fo:layout-master-set>

<fo:layout-master-set>
<fo:simple-page-master master-name="simple"
page-height="29.7cm"
page-width="21cm"
margin-top="1cm"
margin-bottom="2cm"
margin-left="2.5cm"
margin-right="2.5cm">
<fo:region-body margin-top="3cm"
margin-bottom="1.5cm"/>
<fo:region-before extent="3cm"/>
<fo:region-after extent="1.5cm"/>
</fo:simple-page-master>
</fo:layout-master-set>
The space for the header and footer is taken from the <fo:region-body /> area. Thus this has to be compensated in the definition of <fo:region-body /> by adding margins of at least the extent of the header (margin-top="3cm") and footer (margin-bottom="1.5cm").
"Basic layout example"