Joozdlog Pilots Logbook Uses (or will use) parts of iText PDF library (https://itextpdf.com/en) This program is open source under AGPL (http://www.gnu.org/licenses/agpl-3.0.html) If you decide to use (parts of) it in your own project, or have any feedback, I would appreciate it if you'd let me know.
installation: Import the whole thing into Android Studio and install onto your phone. (if you need more installation instructions than that, I suggest not doing it; you're giving quite some control to your device to whatever you are running by installing anything in this way) It is also in the Google Play Store (for free at the moment)