I found a workaround within the framework. There are two steps to this:
Step 1:
Add the line of code $cellspec['text'] = str_replace ( "<br>", chr(10), $cellspec['text'] );
in the function detailView_multi (&$dbobject, $zone, $current_row)
just below the line $cellspec['text'] = str_replace(' ', $nbsp, $cellspec['text']);
in the file std.pdf.class.inc
Step 2:
In the cell where one wants to introduce the line break you can introduce the string "<br>" such that for example if you want to print "hello world" but with a line break then you would have to modify the text string to "hello<br>world".