Increasing margins of all pages in a pdf file


I need to increase the top and bottom margins of all the pages in a pdf file, or alternatively increase the size of each page so as to add a little white space at the top and the bottom. How can I do this?

The pdf is not cropped so it is not a matter of decreasing the crop.

I have Adobe Acrobat Professional 9.

EDIT: The pages in the pdf files have different sizes, and I need to keep it that way. What this means is that I can't just change the page size, cause that would produce a pdf file with all pages of the same large size. What I need is to add a small differential of size to each page separately.

Best Answer

Here's what I ended up doing: I added a thin Header/Footer to every page with Adobe Acrobat Pro 9. There's an option in the Header/Footer dialog that compresses the contents of every page to make space for the header/footer, which is exactly what I wanted.