MuPDF is a free and open-source software framework written in C that implements a PDF, XPS, and EPUB parsing and rendering engine. In Gentoo, several packages like app-text/llpp or app-text/zathura-pdf-mupdf use it internally for PDF rendering.
Users can install MuPDF with the following command:
emerge --ask app-text/mupdf
The app-text/mupdf package provides the following binaries:
MuPDF is said to provide optional support for interactive features such as form filling. However, documentation of these features seems well hidden.