No, it won't void your warranty.
However I would highly suggest getting a micro-fiber cloth to place over it to protect the screen as this film you want to use may (or may not) leave permanent marks on your screen (due to chemical byproducts used in its manufacturing process).
You can get one here:
http://www.radtech.us/Products/NotebookScreenSavrz.aspx
I have that. But I haven't been using it. Do you have first hand knowledge that the PalmGuard is bad for the screen? What are the signs?