class BaseCellElement, method LoadAlign and LoadVAlign
when value in switch () will be other then specified in cases (default:)
Exception will be raised because string.Format requires one parameters but it 
does not provided:

Debug.Fail(string.Format("TableRowItem.Load - Unknown alignment {0}"), 
xVAlign.Value);

should be like this:
Debug.Fail(string.Format("TableRowItem.Load - Unknown alignment {0}", 
xVAlign.Value));

I'd like to participate into this project because I almost finished similar 
functionality for my own internal project.

When trying to get the type of object SubTitleItem
returns the wrong type (ParagraphItem)
For each item in Section.content
If TypeOf(item) is ParagraphItem Then
MsgBox(item.GetType.Name.ToString)
ElseIf TypeOf(item) is ImageItem Then
MsgBox(item.GetType.Name.ToString)
EndIf

If the current array element type will SubTitleItem it still falls into the 
condition is ParagraphItem