Adobe printer problem

I use windows 7 and when i chose the adobe printer from within microsoft word ( printing a word document created by the OCR software Nuance Omnipage) i get a pdf centered horizontally but not vertically ( the content is scotched to the upper part of the page).

I'm missing thus a top margin.

I cannot create the top margin from withing Word because it would have to be done manually for each OCR output word file ( i have hundreds of them).

I've tried creating a top header from within Adobe acrobat pro X, but it won't work. Redimensionning the page to a higher format within the crop tool in Acrobat results in the same problem.

How do i center the content so i get too a top margin ?