Table Class
I had a look at the boxable class for Table. It looks as if these are the only styling options you have ( atleast according to this class ) :
public Table(float yStartNewPage, float pageTopMargin, float pageBottomMargin, float width, float margin,
PDDocument document, boolean drawLines, boolean drawContent, PageProvider<T> pageProvider)
See: https://github.com/dhorions/boxable/blob/master/src/main/java/be/quodlibet/boxable/Table.java
I see though that also HTML can be included, so maybe you should try using html formatting such as: e.g. <table bordercolor=”red”>
Cell Class
Cell class seems to have a LineStyle .
So it would make sense that in the following code (taken from unit test), you would be able to do additional actions.
Cell<PDPage> cell = headerRow.createCell(100, "Awesome Facts About Belgium");
cell.setFont(PDType1Font.HELVETICA_BOLD);
cell.setFillColor(Color.BLACK);
cell.setTextColor(Color.WHITE);
cell.setBottomBorderStyle(new LineStyle(Color.RED, 2));
table.addHeaderRow(headerRow);