Popular Open Source PDF Readers
Advertisement
Reading, annotating, and signing PDFs doesn’t require a recurring Adobe Acrobat subscription — a small set of mature open source tools covers everyday viewing, quick reading, and handwritten markup without one. Okular, KDE’s universal document viewer, is the broadest of the three: it reads PDFs alongside ePub, comics, and several other formats, and adds full annotation and digital signature support in the same app.
Sumatra PDF takes the opposite approach, aiming for the smallest and fastest Windows-only viewer possible rather than a feature-rich suite — a good fit for anyone who just wants a PDF open in under a second. Xournal++ is built specifically for pen and tablet input, layering handwritten notes and markup directly over a PDF background, making it the natural choice for anyone annotating documents with a stylus rather than a mouse and keyboard.
Advertisement
Popular Open Source PDF Readers
Okular
KDE's universal document viewer
Okular is a free, open source universal document viewer from KDE that reads PDFs, ePub, comic books, and more, with full annotation and digital signature support.
Sumatra PDF
Lightweight, open source PDF reader for Windows
Sumatra PDF is a free, open source PDF, ebook, and comic book reader for Windows built for minimal size and near-instant startup rather than editing or annotation features.
Xournal++
Open source handwritten notes and PDF annotation app
Xournal++ is a free, open source handwriting and note-taking app with PDF annotation support, built for pen/tablet input and precise markup on top of existing documents.