To organise PDFs in iBooks on your iPad

1. Under Collections, select + New Collection
   
2. Enter a name for the new Collection, in this example Science, then press anywhere else on the screen to return to your PDFs
   
3. Choose Select then press the PDFs that you want to move. When you have blue ticks on all of the PDFs you want to move, select Move
   
4. Press the collection you want to move them to, in this example Science