Okular review

Okular is the document viewer from KDE, released under the GPLv2+ license and updated with each KDE Gear release; version 26.08 shipped in August 2026. It is not a full editor, because it cannot change a PDF's original text, but it covers two of the most common tasks for Linux users well. Annotation mode adds inline and popup notes, highlights, underlines and your own text. Signature support lets you view and verify digital signatures embedded in PDFs, see whether a file changed after signing, and sign PDFs yourself with a certificate. Okular also opens EPub, DjVU, Markdown, comics and images, and includes thumbnail and contents panels for long files. It installs from Discover, GNOME Software, most distribution stores or Flathub, and on KDE desktops it is often present already. For anyone who just needs to mark up and sign documents, it costs nothing and adds no watermarks.

Who it is for

Linux users who mainly read, annotate and sign PDFs and want a free, preinstalled-feeling tool.

Price

Free and open source (GPLv2+).

and is thus fully Free Software
Quoted from the vendor pricing page on November 10, 2026.

Key features

• Annotation mode for inline and popup notes, highlights, underlines and added text
• View, verify and create digital signatures in PDFs
• Opens PDF, EPub, DjVU, Markdown, comics and common image formats
• Thumbnails and contents panels for moving through long documents
• Available from Discover, GNOME Software, distribution stores and Flathub

Strengths and weaknesses

• Strength: Free Software under GPLv2+
• Strength: Often already installed on KDE desktops
• Strength: Certificate signing and signature checks built in
• Weakness: Cannot edit the original text or images of a PDF
• Weakness: No page reordering or merging tools
• Weakness: Fits best on KDE Plasma desktops

Key facts

• License: GPLv2+
• Latest release: Okular 26.08, August 2026
• Install: Distribution packages, Discover, GNOME Software, Flathub

Where it ranks

Okular is No. 4 in our Best PDF Editors for Linux verdict.