Common Annotation Types
- Highlight — color a text span to mark important passages (yellow, green, pink)
- Pen / freehand draw — circle elements, draw arrows, underline with emphasis
- Text note / sticky note — add a comment anchored to a position on the page
- Rectangle / shape — box a section to draw attention to it
- Stamp — pre-built marks like "Approved", "Rejected", "Sign Here"
PDF Annotation Standards
The PDF specification defines annotation types as standard objects. Highlights, notes, and drawings created by Acrobat, PDF.js, or any compliant tool are stored in the same format and visible in any PDF viewer — you're not locked into one app.
Flatten Annotations Before Sharing
Annotations stored as objects can be deleted by the recipient. If you want your marks to be permanent (for a reviewed document you're returning), flatten the annotations into page content before sharing. Use Flatten PDF after annotating.
Text Selection vs. Pen Tool
Highlighting requires a text layer (the PDF must have selectable text). For scanned PDFs without text (image-only), use the pen tool to draw freehand over the image, or run OCR first to make the text selectable.
Review Workflows
- Annotate with highlights and pen marks
- Add sticky notes for specific comments
- Export with annotations intact — send to author
- Author addresses feedback, then flattens final version
Annotate a PDF Now
Open ToolsVito's PDF Annotator, mark up your document with highlights and drawings, and export — all in your browser.