Channel 4 is updating its 4oD service, offering new features, but perhaps also hitting you with more ads as you watch.In an official statement, the broadcaster claims 4oD is the UK's most successful commercial video on demand service, reaching 'nearly one third of all young people in the UK on a monthly basis'. But that's obviously not enough, hence the update.The 4oD apps for both iOS and Android will be updated in 2013, with the headline feature being free ad-supported offline viewing, meaning you can download and watch many of your favourite Channel 4 shows, on catch up and on the move on a smartphone or tablet.The new apps will also feature ‘Pause and play' across platforms, so you are able to pause a programme on 4oD on one platform and then resume watching from the same point on another device. Finally, C4 ‘Watch live' on mobile devices will be introduced, with all of Channel 4's main channels available to watch live on iOS and Android devices.Free all the way, but ad-support is definitely key here. In 2013 Channel 4 will also launch a new digital ad product, Adapt, which will enable advertisers to target logged on users based upon their age, gender and location. So be prepared to be hit with ads as you watch your favourite C4 shows using your personal data. That's the price of 'free'.Commenting on the new service, Channel 4's Commercial & Business Development Director, Sarah Rose said: 'We're very excited to be the first commercial public service broadcaster in the UK to offer mobile offline viewing, enabling our viewers to catch up with Channel 4 wherever they may be.'And the introduction of ‘Watch Live' on the move and cross platform ‘Pause and Play' is great news for our young-skewing audience who are increasingly watching our content on multiple mobile devices. These new product innovations both reward our registered viewers and further strengthen our viewer engagement strategy.'When the apps are available, we'll let you know. But still at least a couple of months off.