Epson Scanner Resizing

[parvardigar]

Hello

I scan booklets to PDF.
I scan at 4" x 6"

When I open the scanned PDF documents in Adobe Acrobat the 4 x 6 sits on top of a 8.5 x11 sheet.
I should see only the 4 x 6 scan.

To fix this I open all the 4 x 6's in Photoshop. In photoshop the scans are all 4x6

I then save as 'PDF'

When I open them in Adobe Acrobat I see the 4 x 6.
If I scan at (rizing in the usual manner) 4 x 6 why is Acrobt showing those scan in a 11x8.5 window?
I do have a Photoshop fix but that is long work around
Thanks!