Turn an A4 book into a LETTER Size Book [for KDP]

I'd like to turn some of my work (worksheets) into a book. Problem is everything was designed in PAGES and everything is currently A4 size. I'd like to upload it to KDP but they dont accept A4 size. I think the closest option is US letter size. I'd like you to resize the pages to fit US letter size and prepare it so that I can just upload it to KPD. The book is around 100 pages. If we agree to work together I'd like to see what it will look like first (a few pages) before we go ahead and do the whole book.