Editing PDF (section)

=== Annotation ===
{{Unreferenced section|date=November 2023}}
{{See also|Comparison of note-taking software}}

Adobe Acrobat is one example of proprietary software that allows the user to annotate, highlight, and add notes to already created PDF files. One UNIX application available as [[free software]] (under the [[GNU General Public License]]) is [[PDFedit]]. The freeware [[Foxit Reader]], available for Microsoft Windows, macOS and Linux, allows annotating documents. Tracker Software's [[PDF-XChange Viewer]] allows annotations and markups without restrictions in its [[freeware]] alternative. [[Apple Inc.|Apple]]'s macOS's integrated PDF viewer, Preview, does also enable annotations as does the open-source software [[Skim (software)|Skim]], with the latter supporting interaction with [[LaTeX]], SyncTeX, and PDFSync and integration with [[BibDesk]] reference management software. Freeware [[Qiqqa]] can create an annotation report that summarizes all the annotations and notes one has made across their library of PDFs. The Text Verification Tool exports differences in documents as annotations and markups.

There are also [[web annotation]] systems that support annotation in pdf and other document formats. In cases where PDFs are expected to have all of the functionality of paper documents, ink annotation is required.