Page Labels let you have page numbers that are Roman Numerals or have prefixes or things like that. If this doesn't sound like something you need, you're probably better off just using muPDF by Artifex which this is based on.
Artifex MuPDF
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A lightweight, high quality PDF/XPS/CBZ/EPUB viewer for Android devices.
The renderer in MuPDF is tailored for high quality anti-aliased graphics. It renders text with metrics and spacing accurate to within fractions of a pixel for the highest fidelity in reproducing the look of a printed page on screen.

MuPDF is also small, fast, and yet complete. It supports PDF with transparency, encryption, hyperlinks, annotations, searching and more. It also reads XPS/OpenXPS documents, and v2 EPUB files with no DRM. MuPDF is written modularly, so features can be added on by integrators if they so desire - contact Artifex for licensing opportunities.

MuPDF is under continual development, so if you find any files that don't work, please let us know by opening a bug report on http://bugs.ghostscript.com/.