You can also change the layout on any one particular page, by making use of the setTemplate action within the relevant handle in the catalog.xml layout file.

If we want to change the product view page's layout to use the left-column layout, then we can change the following XML in catalog.xml under the catalog_product_view (non-default) handle:

<reference name="root">
<action method="setTemplate">
<template>page/2columns-right.phtml</template>
</action>
</reference>

All that we need to change is the word right to left:

<reference name="root">
<action method="setTemplate">
<template>page/2columns-left.phtml</template>
</action>
</reference>

Once the page is refreshed, the product view page will now be displayed with the column to the left.