[any ANONYMOUS forum user]

1. Download a .PDF ebook file onto your computer.
2. Open iTunes and select "File" -> "Add to Library…" from the drop-down menu (Or just drag-n-drop your PDF files onto iTunes).
3. Select the .PDF file that you want to transfer to your iPad/iPhone/iPod Touch. Click Choose and the PDF eBook file will be added to your Book Library in iTunes
4. Sync your iPad with iTunes and the ePub book will show up in iBooks.

Note that if your PDF ebook is DRM protected, you need to remove DRM protection before adding your ebook to iTunes.