NightPDF
NightPDF is an application that allows you to read PDF files in dark mode. Free and open source program
Master PDF Editor
Master PDF Editor is a free and multi-platform, easy-to-use, but powerful and multifunctional program for working with PDF documents
Boomaga
Boomaga is a virtual printer for viewing a document before printing it out using the physical printer
qpdfview
qpdfview – free and open source software for viewing PDF documents with tab support
Okular
Okular is a free and open source, multi-platform document viewer that supports a variety of formats
Evince
Evince is a free and open source program for viewing PDF documents, comic books, and others.