How do I make a non-proportional shrink of a pdf page?

I have an 8.5 x 11 page that I need to shrink to a 9.25 x 7.5 page to use for a perfect bound book that is not 8.5 x 11. This is not a proportional shrink. So one dimension will get slightly distorted, but it's very close. If I print to the pdf printer, it leaves white space along the sides of the page rather than stretching the image horizontally to the edges of the page. I can do all this in Photoshop for each page, but that takes a long time for a 50 page book. I bought some software that lets me change to size to a non-traditional size, but the length-width proportion is still the same as before, and that leaves the white borders on both edges of the page.

Is there a way to do a non-proportional shrink of a pdf page so that the narrower part of the conversion stretches to met the edges of the new size rather than leave white edges?

Thanks,

Clark