Write some Software

I need someone to modify the WHMCS template "[login to view URL]" that handles PDF generation. I need the template to use a format compatible with a standard #10 double windowed envelope. The company logo/return address being displayed in the top window and the client's mailing address being displayed in the bottom of the window. Beyond that, the template can remain mostly the same as long as the standard invoice fits on to 1 page (normal amount of invoice lines of course).