Generally, allow more straightforward setters of style related properties without going through 2-4 levels of temporary objects.  For example, when dealing with tables, there is no obvious way to set line spacing or paragraph spacing globally for the table.  Should have TableCell.Blocks.AddText("New Text") instead of AddParagraph, which provides spacing you don't want or need.

Also, when you want to set the FontSize, FontWeight, and FontFamily all at once, there is no easy way to do that.  Also no global way to do that for a section, page, table, etc.

The above would make it a LOT easier to create documents programmatically.  I would like to see more parameterized constructors for common style attributes by type.  You will discover the challenges by creating a richer document from scratch with several tables, styles, left and right justified content on the same line, etc.  Same for easily setting header and footer content.

Thanks!  Great work so far, I love it!