Okular

Okular reads PDFs plus EPUB, DjVu, CHM, comics, and more, and covers the Acrobat Reader jobs that matter: highlighting and annotation (saved into the PDF itself), form filling, digital signatures, and text extraction. It’s fast on huge documents and its annotations are compatible with other standard readers.

It won’t edit PDF content — rearranging pages is PDF Arranger’s job, and rewriting text needs a real editor like LibreOffice Draw or a paid tool. Some aggressively non-standard forms (XFA, common in government paperwork) render poorly, which is an upstream Poppler limitation shared by most Linux viewers; keep a fallback plan for those. On GNOME it drags in KDE libraries, where Evince or Papers is the lighter native pick.