On the Tools toolbar is the Zoom tool.
This tool allows you to zoom in and out of particular areas of your page in the main editing window.
Select the Zoom Tool by clicking on the toolbar button. The cursor will change to a magnifying glass.
You can click on your page with the left mouse button to zoom in to that area to the next preset factor.
You can click with the right mouse button to zoom out the next preset factor.
You can click and drag the tool to surround the area you want to magnify and Opus will zoom in using the appropriate magnification up to the maximum zoom level of 1600%.
There is also a Zoom option on the View toolbar which lets you specify the overall magnification of the page.