While debug builds are ok for debug are TOTALLY NOT OK to run them in a production environment. They're a lot of slower, a lot thicker and each transitition between the file manager and the reader will be, at least, 2x slower. Version updates will take about 4-5x time too.
Much better to build a release APK and sign it. The easiest option is to use
https://github.com/patrickfav/uber-apk-signer
Something like
Code:
uber-apk-signer -a path/to/app.apk
should produce a path/to/app-aligned-debugsigned.apk that's installable.