In addition to its primary textual content, a PDF file can contain annotations that represent links, form elements, highlighting circles, textual notes, and so on. Each annotation is associated with a specific location on a page and may offer interactivity with the user. Annotations allow users to mark up and comment on PDFs without altering the original author's content.

ComPDFKit PDF SDK supports most annotation types defined in PDF Reference. ComPDFKit PDF SDK provides APIs of annotation creation, properties access and modification, appearance setting, and drawing.

Annotation Types


ComPDFKit PDF SDK supports all common annotation types:

- Note

- Link

- Free Text

- Shapes: Square, Circle, and Line

- Markup: Highlight, Underline, Strikeout, and Squiggly

- Stamp

- Ink


These are standard annotations (as defined in the PDF Reference) that can be read and written by many apps, such as Adobe Acrobat and Apple Preview.