The problem you are seeing there is that the line will be contained in a section (possibly the details section?) and so will only be printed where that section has data. That is to say that the blank area underneath the last line item contains data and therefore no sections, so nothing is printed there and there is no line extending in to that area.

To achieve what you are trying to do with the lines extending the whole page you would need to create a template (File -> New -> New Template) and draw the lines on that. A template will contain a single detail section which will span the whole height/width of the page so simply draw lines of the desired height and location on this. I would actually recommend placing all of the 'layout' elements such as the image and other boxes/lines on the template. Once you have created a template you can apply this to your layout by setting it's template property (View -> Properties if this is not already visible).

Hope that helps

Thank you Darron, I will try to create a template as per your instructions and report the outcome.