Create PDF from scanner - letter - legal

Hello,

everytime i want to create a pdf from a scanner i get a legal page. But i need letter. Of course i can show up the scanners native interface. But it is always behind the windows. The only chance to get it in the front is the taskmanager.

I have to do it every time.

I checked all settings on the printer, pdf printer, driver... Everything is configured with standard paper size letter.

Is there something like a registry configuration to fix this issue?

I use Adobe Acrobat Pro XI and Windows 7, 64 bit

Thank you very much!