Firefox PDF Viewer (PDF.js)
Open Source
PDF.js. A general-purpose, web standards-based platform for parsing and rendering PDFs.
EPUBReader
Free
EPUB is an e-book file format with the extension .epub that can be downloaded and read on devices like smartphones, tablets, computers, or e-readers.
Compare Sumatra PDF with alternatives
Compare Firefox PDF Viewer (PDF.js) and Sumatra PDF and decide which is most suitable for you.
Compare EPUBReader and Sumatra PDF and decide which is most suitable for you.