Custom margins for each page possible?

I am using the latest version of acrobat on windows 7 64 bit.I just got a new tablet and would like to optimize the pdf file the way i want for reading purposes.I have a book which has many pages of different width and height.After using the remove white space tool,i would like to add certain amount of white space at the top and bottom of each page.But i can find an option to only set a fixed page size for all pages.Is there a way i can add fixed amount of white space to each page without having to separately edit them all?

Thanks in advance!!!!!!!