I used to write a similar app. I posted my AndroidManifest.xml segment for your reference:
<activity
android:name=".OpenFileActivity"
android:configChanges="orientation|keyboardHidden"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.VIEW" >
</action>
<category android:name="android.intent.category.DEFAULT" >
</category>
<category android:name="android.intent.category.BROWSABLE" >
</category>
<data
android:mimeType="application/pdf"
android:scheme="file" >
</data>
</intent-filter>
<intent-filter>
<action android:name="android.intent.action.VIEW" >
</action>
<category android:name="android.intent.category.DEFAULT" >
</category>
<category android:name="android.intent.category.BROWSABLE" >
</category>
<data
android:mimeType="application/pdf"
android:scheme="content" >
</data>
</intent-filter>
<intent-filter>
<action android:name="android.intent.action.VIEW" >
</action>
<category android:name="android.intent.category.DEFAULT" >
</category>
<category android:name="android.intent.category.BROWSABLE" >
</category>
<data
android:host="*"
android:pathPattern=".*\.[pP][dD][fF]"
android:scheme="file" />
</intent-filter>
</activity>