In order to Pin from an iPhone or iPad in Safari, you'll need to install the Pin It button:
- Open up Safari and go to http://www.pinterest.com
- Add a bookmark by tapping the icon that looks like a box with an arrow coming out
- Select "Bookmark" and change the title to "Pin It". Tap "Save"
- Tap the icon of the open book and select "Edit and then "Pin It"
- Beneath the title, you'll see a box to add the bookmark's address - delete the "www.pinterest.com" and paste the following code: