Just a FYI there is a help just type "lrf2lrf -h" from the command line and the help page will print.
There are two ways to change the fonts.
First if you know the exact font size you want to change type this command.
lrf2lrf -f 100,150 MyeBOOK.lrf
The "100" is the existing 10pnt Fonts that you want to change. The "150" (15pts) is the new font size you want for the book.
100 = 10pts
150 = 15pts
Note this will change every 10pts to 15pts
Second is a tad harder, but very doable. You have to find the TextStyle uinqie ID. There is a uniqe ID for each font style in the reader. This is done by typing the following command
lrf2lrf -e MyeBOOK.lrf
What gets displayed is the listing below
Note the text that occures the most is TextStyle ID 317
it also has a font size of 80 (8pts)
TextStyle ObjId=310 Fontsize = 160
TextStyle ObjId=315 Fontsize = 110
TextStyle ObjId=317 Fontsize = 80
Recommend TextStyle = 317
Found TextStyle = 315 Occurrence = 14
Found TextStyle = 363 Occurrence = 2
Found TextStyle = 317 Occurrence = 79
Now that you have the TextStyle ID (objID) and the Font sizes. Determine which is the one you want to change and pass the ID with the new font size as described below
lrf2lrf -x <TextStyle ID> -s <My New Font size> MyBook.lrf
If my explanation does not clear things up.
Please run lrf2lrf -e <your LRF book> and post the output on the board.