Is it possible for PDF Formatting to underline each row?

Yes it is possible, there are formatting options to accomplish this; however, formatting applied to a row definition will apply to all members within that row definition.

Another option is to import the relevant data or view into a Dashboard Component of type Report, which (from version 6.3) allows for WYSIWYG "pixel perfect" editing of reports. This functionality is also available in Report Studio for older versions.