The price will fall. Today the iPhone can be had for $99, down from $599 when originally released.
You're right about pdf format. I love pdf for its 'portability' in my business.
A couple of years ago all of our invoices were sent and received via FAX.
I'd say that 98%+ are now done via e-mail in pdf format.
And with a free app like BullZip:
Sure makes "doing business" easier, quicker, and a damn sight more efficient.