If you are merging data with your form when you render it, you could include the FormPreference parameter (PDF or PDFForm) in the data, then check that value on the initialize event of the form. Based on the value, you can hide or show the buttons. There's probably another way, but nothing springs to mind.
You'll probably have better luck posting your question in the LiveCycle Forms forum.
Jared Langdon
www.jlangdon.ca