Adobe Reader is the free undisputed leader application for reliable interaction and visualization of PDF files on Android phones and tablets.

AirDroid allows you to access your Android phone/tablet and manage it via wireless from Windows, Mac or Web, viewing on a computer screen calls, text messages, contacts and application notifications. In this way you can use keyboard and mouse to perform multiple tasks, such as transferring files, photos, videos, music, ringtones and obviously applications APK files.

Automatic Call Recorder allows you to record your calls. You can set which calls to be recorded and which ones to be ignored, listen to the recording, add notes and share it. Integration with Google Drive (only for Android 3.0+) and Dropbox also allows you to save and synchronize your calls in cloud. It’s also available in the Pro version, but as call logging does not work with some phones and can result in a lower quality recording, you should try the free version before buying the paid one.

Battery Doctor (Battery Saver) is a free application that promises to save battery power for devices on which it is installed. Although it is well known that task-killer are worthless on Android, other functions such as management of connectivity and brightness, ability to see which apps consume more and recharge history, can certainly help to increase device battery autonomy.