Xpdf is a viewer for Portable Document Format (PDF) files.

Xpdf is designed to be small and efficient.  It runs under X, using
the Motif libraries.  It can use Type 1, TrueType, or standard X
fonts.  Use of the T1 library provides superior rendering of Type 1
fonts, and also permits run-time configuration of the exact fonts
to be used.

Homepage:
https://www.xpdfreader.com/
