Changing the page size of an existing PDF

Hi,

I did an interactive PDF a month ago, with a lot (330) PDFs a client gave me. I had to bookmark each page, so you can navigate through them.

The problem now is that each page has a different size:

- 210 x 297 mm

- 320,3 x 443,3 mm

- 500 x 700 mm

... (And more)

And my client has problems trying to print the document...

Is there a way I can reduce the size of ALL the pages to 210 x 297 mm (For example) but NOT CROPPING the pages, just adapting the content of each page to that size... Is it possible?

And not losing all the bookmarks I did...

Thank you a lot.

Best regards,

Daniel.