https://okular.kde.org/
Okular - The Universal Document Viewer
Multi-platform, fast and packed with features, Okular allows you to read PDF documents, comics and EPub books, browse images, visualize Markdown documents, and...
okularuniversaldocumentviewer
https://api.kde.org/legacy/okular/html/index.html
Okular - Okular, the unified document viewer
KDE products API documentation
okularunifieddocumentviewer
https://eco.kde.org/blog/2022-03-16-press-release-okular-blue-angel/
First Ever Eco-Certified Computer Program: KDE's Popular PDF Reader Okular - KDE Eco
Press release to announce Okular receiving the Blue Angel eco-label.
first evercomputer programpdf readerecocertified