You can use the PDF Plugin for GitdenReader only when GitdenReader is installed on the device. After you install this, you should run Gitden Reader first and then open .pdf file.
If you run this plugin alone, just a popup window appears and then the app is closed.
PDF Plugin for GitdenReader is based on the MuPDF library. It is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or any later version.
Source code available at https://github.com/gitden/pdf-plugin/