This is a common issue with older systems. First, try restarting your device. If that doesn't work, go to Settings -> Apps -> find your PDF reader, and clear its cache. If the problem persists, uninstall the app and try a different, more lightweight PDF reader from the list above.
Here’s a deeper look at each recommended app to help you choose the right one. Pdf Reader Apk Download For Android 4.4.2
