Tweetbook.in is the latest service to help you archive your tweets. Unlike most, Tweetbook saves your tweets in PDF format for easy reading and sharing. The services not only supports your tweets, but also your favorites. You can even share the PDF files right from the service. Tweets seem to go back only as far as a week, though this could be dependent upon how much you’re tweeting and how many tweets the service is able to pull due to API restrictions.