iPad app to convert multiple photos to a single pdf
Even simpler than Pages, you can use iBooks


Step 1: Select all photos you want to combine into one pdf within
your Camera Roll, they should be in the order you want them combined
in 
Step 2: Press the share button (the up arrow in the box at the
top left hand corner of the screen) 
Step 3: Tap iBooks icon prompting to "Save the PDF file in iBooks"


That's it!