How to sync iBooks PDFs from my MacBook to my iPhone?

I have 26 book PDFs on my laptop but they won't show up on my iPhone. How can I get them to show up so I can't only read on my laptop, but also on my phone? They won't show up under "PDFs" or "purchased books" or "books" or anywhere.

Added (1). I have the iBooks app on both devices and they won't sync. Maybe through iCloud? But I don't know how to do that. I read somewhere I need to do something with iTunes but I'm not sure how?

You would have to have bought them through the iBooks app.

http://support.apple.com/.../kb/HT5826

To copy non-purchased files, see the options below.
EDIT:

iYunes keeps every iBook in its list of purchases for you. Nothing is needed to get it to sync, unless you have changed syncing to manual instead of the full sync. "Having" the iBooks app doesn't make your PDFs that were not bought through iTunes sync. You have to buy the iBooks through iTunes. As I said, use one of the solutions below to copy non-Apple files to your iPhone.

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