It replaced KPDF, its main predecessor, alongside KGhostView, KFax, KFaxview and KDVI in KDE 4.

Okular was started for the Google Summer of Code of 2005 by Piotr Szymański.

[5] In this season, the Okular toolbar mockup was created based on an analysis of other popular document viewers and a usage survey.

[7] In December 2020, the software versioning scheme was changed from sequence-based identifier to CalVer.

[8][9] Okular's annotation features include commenting on PDF documents, highlighting and drawing lines, geometric shapes, adding textboxes, and stamps.