This behavior might be encountered because you didn't properly selected paper to be used. If you didn't properly select the paper, while printing the two columns, these might get deformed. Also, I suggest that you create the columns in two separate text wrappers. By doing this, you can make sure that you properly set the border between them to a minimum of 5 mm. This should be enough to make a visible difference. To set the space from border, double click on the text wrapper, and choose proper values for right and left spaces under Borders zone.