Branchfire’s excellent iPad app iAnnotate PDF has just gotten another update, promising better file synchronization and management features.

Released way back in April 2010, iAnnotate PDF continues to be a hit among users. Branchfire claims to have served hundreds of thousands of users with iAnnotate PDF, and it’s not hard to see why users choose it over other apps of its kind.

It’s a PDF annotation app that’s not only feature-rich but also easy-to-use. It just makes handling PDF documents a breeze.

And thanks to its latest update, iAnnotate PDF now renders PDFs more smoothly than ever. PDFs can be really heavy-handed at times, so the app’s ability to better project speed and responsiveness while scrolling or zooming is most welcome.

If you can’t see the video embedded above, please click here.

The app now also supports OneCloud, Box’s collaborative app suite. After marking up your PDFs, you can already take advantage of OneCloud’s “round-trip” file editing and syncing feature. In line with this, iAnnotate PDF’s syncing capability with Box and other supported services has been improved by the update.

Also featuring a new library interface that presents files both local and remote in one place, iAnnotate PDF is available in the App Store for $9.99.

Don’t let its unusually high price keep you on the fence. Just read our original review of the app or watch Bloomberg TV’s interview with Branchfire CEO Ravi Bhatt above to see what else iAnnotate PDF has in store.