As mentioned in my post earlier today, Adobe Lightroom has come to the iPad in the form of Lightroom Mobile. If you are an Adobe Creative Cloud subscriber, the app is free. You download it from the App Store, sign in with your Adobe ID and you are ready to go if you have also updated your Mac version of Lightroom to the just-released version 5.4.
Lightroom is based on collections, and any collection on your Mac can be quickly synced with the iPad version. Lightroom Mobile works with Smart Previews, the compressed DNG format files that Adobe added as a feature in Lightroom 5. On your Mac, your files are full size RAW format. You work on the Smart Previews on your iPad.
Changes you make on your iPad are synched back to the full size versions on your Mac. The same is true the other way. Make an edit in a photo in a synced collection, and presto, the change appears on your iPad. It's best to do this over WiFi for speed, and so you are not running over any cellular data allotments you may have.
Think of Lightroom Mobile as a remote extension to your Mac files. The app needs that Internet connection for updates to work, but you can edit files without an Internet connection and sync them when you're connected.