Use Backspace key to delete to the left and Delete key to delete to the right. That is if you have a full keyboard layout. On iBooks there isn't a delete key, keyboard is without two additional sections for navigation and for calculating. And it may be annoying.
This isn't really a Pages question, but a general Apple Mac tip. I'm only publishing this in praise of elbow grease, an age old remedy for almost any problem.
Press and hold fn, hit Backspace and you delete to the right
Press fn+Option, and Backspace deletes text word by word
For a long time I've been looking for a way to delete both to the right and to the left on a shortened laptop keyboard where there is only a Backspace key which deletes to the left, but no Delete key as on bigger keyboards, which deletes to the right. I've tried this and that, looked up in manuals and in help sections and couldn't find a solution. Until I decided to sit down and devote a long session to just this - finding out how to delete to the right on my iBook. After trying dozens of combinations I found it: the little 'fn' (funny) key - last on the left in the bottom row of the keyboard. Press and hold, hit Backspace and it works like the Delete key on the big keyboard - deletes to the right.
Used with Option key (alt) Backspace deletes text word by word, with fn+Option Backspace deletes word by word to the right.