Our Print-Ready PDF export capability has all the sizes you need for a print book on KDP and most other print-on-demand services.
So, you can match your Print-Ready PDF export size on Leanpub to the size you need for KDP or any other service you're using to get your book into print, and then you can export the appropriate Print-Ready PDF from Leanpub.
Sometimes people ask us for guidance on this matter. Articles by successful authors like this one can be really helpful. You can also search our Authors Forum or post a question to the author community there.
Here is what Leanpub co-founder Peter Armstrong once wrote in an exchange with a Leanpub author:
"I've never used KDP myself, but my teenage son wrote a sci-fi novel on Leanpub, and then published it on KDP. I didn't help him with the KDP part at all, and he made his wraparound cover in Sketch and I think Amazon got the ISBN for him. Our print-ready PDF export worked fine for him, but his initial export used fonts and a page size which were too big for a fiction book.
So, what I would recommend is:
Do a Print-Ready PDF export of your Leanpub book.
Look at the PDF in preview in 1-page and 2-page mode and see if you're happy with it. Ask yourself if the font size should be smaller or larger. For example, with my son's novel, his initial export used a page size and a font size which was too big. So, I did help him with choosing export print-ready PDF settings, and we ended up choosing 8.5 point font, 1.2 line spacing, digest page size, 1.25 inch inner margin, 0.75 inch outer margin, 0.5 inch top margin, 0.5 inch bottom margin, 1.25 line paragraph spacing, etc. For your book chances are you would want at least 9 point font, and a Technical page size (7.0" x 9.1") or similar.
Go through the KDP process and then order one print book and check whether you would be happy with the font sizes, etc."