Primary Uke
If you are downloading Primary Uke onto your iPad, you'll need a powerful iOS app like Good Reader (AUD$7.99) as the file is zipped and iPads need external help to unzip!

Don't forget to save your downloaded files somewhere you can access them again if you purchase them on an iPad. Below is an option to save PDFs (but not the other files you receive with Primary Uke)

How to transfer PDF eBooks to iBooks (on iPads)
A PDF file you have downloaded from a website can usually be opened in the browser window on your iPad and then be transferred to the iBooks app on your iPad.

1. Make sure the free iBooks app is on your iPad.
2. PDF document opens in web browser on your iPad.
3. Tap once on the document.
4. Look for the “Open in iBooks” button to appear in the upper right.
5. Tap the button and the PDF will be added to your iBooks collection on your iPad.
From now on, you can open the PDF document from the iBooks app on your iPad.

(thanks to ipadacademy.com)