CuprumPDF is a PDF viewer based on pdf.js, which is currently the only PDF renderer written in a memory-safe language. It doesn't require any permission: the PDF to be visualized is passed to the app using Content Providers.
This is a fork of PDF Viewer from CopperheadOS made before the license was changed from Apache 2.0 to Creative Commons Attribution-NonCommercial-ShareAlike, which is not a Free/Libre Software license due to the NonCommercial clause. The credit for the idea and implementation goes to the original author.
Pull requests are welcome. Please don't submit feature requests if you're not willing to contribute with code; I'm not an Android developer, so I won't implement them. Do not rip off non-free code from Copperhead's repository. The licenses are not compatible, so new features have to be written from scratch.