Customer with mixed pdf files, letter and ledger, when he prints the letter comes fine and it prints 1 page ledger then the message comes on screen saying A3 not available press continue! the customer does not want to hit continue, played with the print drivers nothing change!!!!

i have run into this a number of times...the paper settings in the copier MUST match those of the paper settings in the driver or the machine can't match up the sizes. Also, if the cursor guides in the copier (from ANY paper source) are off by just a little bit and not tight against the paper, the machine will think there is different sizes in there as well. sounds weird but this has happened many times as well.

I have seen this on fax equipped models also, if the cassettes are hard set in the system menu, the machine doesn't know what to do, it just errors and says the same thing you describe.
Try setting the cassettes to AUTO in the system menu.