Please read my answer to the question How to draw a rectangle around multiline text for which I've written DrawRectangleAroundText.
In this example, we have a Paragraph with plenty of text:
Paragraph p = new Paragraph("This is a long paragraph that doesn't"
+ "fit the width we defined for the simple column of the"
+ "ColumnText object, so it will be distributed over several"
+ "lines (and we don't know in advance how many).");
And we distribute this paragraph over different lines like this:

For this purpose, we use the ColumnText class:
ct = new ColumnText(cb);
ct.setSimpleColumn(300f, 500f, 430f, 780f);
ct.addElement(p);
ct.go();
This is only a simple proof of concept. For more info about ColumnText, read the section Absolute positioning of text in the free ebook The Best iText Questions on StackOverflow. This way, you'll be able to avoid posting a question that can be answered by recycling an answer that was posted less than a day ago.