Android: It's not exactly difficult to view PDFs in Android -- you can use Google Drive, Google's new standalone viewer, or countless other apps. But if you're a Dropbox user and regularly work with PDF files, the addition of a native PDF viewer in the latest version could be helpful.
The Android app has also added in-document search for PDFs, Word documents and PowerPoint files. Dropbox says it is rolling out to the Play Store over the next few days.
New on Android: PDF viewer and in-document search [Dropbox Blog]