To make things simple I will use examples from

http://itextsharp.sourceforge.net/tutorial/index.html

If the following code is used

http://itextsharp.sourceforge.net/examples/Chap0501.cs

You will get the following PDF

http://itextsharp.sourceforge.net/examples/Chap0501.pdf

There is too much empty/wasted space above the data. I would like to reduce the height of the cells so I can fit more on the page. How/can this be done?

I have tried

aTable.DefaultCell.VerticalAlignment =Element.ALIGN_TOP

but it doesn't move the data to the top of the cell, it's as if it doesn't realize that the space is there.

Ah, you are actually trying to fiddle around with the margins, refer to

http://itextsharp.sourceforge.net/tutorial/ch01.html

on how to change the margins

I am trying to change the "cell" top margin not the "page" margins

Apologies, in this case you should be looking at cellpadding, cellspacing and the like

http://itextsharp.sourceforge.net/tutorial/ch05.html

the sample code is at

http://itextsharp.sourceforge.net/examples/Chap0506.cs

 Sorry, my reply sounded a bit rude. It was unintentional.

I was able to get a usable result by changing

cell.Leading = 6;