You can transfer the PDF file to your iPad and nook and it will look fine. I do that all the time.
I am working on formatting everything in .mobi (kindle) and .epub (nook and other readers) as well as the PDF files which can be read on all computers and readers except the Kindle. Formatting for the specific reader just makes them look a little prettier on the device.
You cannot download the files directly to your nook or Kindle, you must put them on your computer first and then transfer them.
The files can be downloaded from your e-mail directly to your iPad or iPhone but you must have apps that will unzip the files and read PDF files.
Okay, time to take off my publisher’s hat (I also own Wil O’ Wisp Publishing) and go paint. My brain is frazzled. ~ JoAnn