How to Add Annotations to a PDF for Free

PDF supports many types of annotations, and different annotation types serve different purposes in a review or markup workflow. Understanding the available types helps you choose the right annotation for each situation. Text markup annotations include highlighting (marking text with a color background), underline (adding a line under text), strikethrough (adding a line through text to indicate deletion), and squiggly underline (indicating an error or question). These annotations reference the underlying text layer, so they only work on PDFs with selectable text — not on image-only scanned PDFs. Comment annotations add text notes attached to a specific location in the document. They typically appear as small icons (speech bubbles or sticky notes) that expand when clicked to reveal the comment text. Comments can be threaded — replies can be added to existing comments — making them ideal for collaborative review where multiple people respond to the same issue. Stamp annotations add graphical stamps to pages: APPROVED, CONFIDENTIAL, DRAFT, REVIEWED, and custom stamps. They are commonly used in business approval workflows to indicate document status. Drawing annotations include free-form lines, arrows, rectangles, circles, and other shapes for marking up diagrams and indicating specific areas of attention. Form field annotations add interactive elements like text boxes, checkboxes, radio buttons, and dropdown lists. These are used to create fillable PDF forms. For document review purposes, the text markup and comment annotation types are the most commonly used.

1. 1Choose the annotation type appropriate for your purpose: highlights for key passages, comments for questions or feedback, stamps for approval status.
2. 2For text-based annotations (highlights, underlines), ensure the PDF has a selectable text layer.
3. 3For scanned PDFs without a text layer, use drawing annotations and comment boxes instead.
4. 4Use consistent annotation styles across a document to make the review easy to interpret.

Several excellent free options are available for adding annotations to PDFs, each with different strengths and appropriate use cases. Adobe Acrobat Reader (free version) provides comprehensive annotation capabilities including all text markup types, comments, sticky notes, stamps, and drawing tools. The free version cannot create or edit PDF content but fully supports annotation. It is available for Windows, macOS, iOS, and Android. For most annotation needs, the free Reader is more than sufficient. Browser-based PDF viewers have improved dramatically. Chrome's built-in PDF viewer supports basic highlighting and note-taking. Microsoft Edge's PDF viewer offers highlights, notes, and drawing tools directly in the browser without any software installation. For quick annotations on simple documents, browser-based tools are the most accessible option. LibreOffice Draw on Windows, macOS, and Linux can open and annotate PDFs. It offers a wide range of annotation tools and can save annotated PDFs. macOS Preview (built into Mac) supports highlighting, notes, shapes, and signatures natively — no additional software needed. For online collaboration, PDF.js-based tools and online review platforms allow multiple annotators to work on the same document simultaneously. These tools are particularly valuable for team document review where multiple people need to add comments and respond to each other's feedback on the same file.

1. 1For desktop annotation: download Adobe Acrobat Reader free, or use the built-in tools in your OS (Preview on Mac, Edge on Windows).
2. 2For browser-based annotation: open the PDF in Chrome or Edge and use the built-in tools.
3. 3For collaborative annotation: use an online review tool that supports multiple simultaneous annotators.
4. 4For professional workflows: consider a dedicated review platform that manages annotation tracking and approval.

Annotations are most valuable when they are part of a structured review process. An ad-hoc collection of random comments is less useful than annotations that follow a consistent approach and can be tracked and resolved systematically. Establish annotation conventions at the start of a review project. Decide which color highlights indicate different categories (yellow = important, blue = question, red = error or change required). Define what types of comments to use for different situations: questions about unclear content versus change requests versus approval notes. Communicating these conventions to all reviewers ensures the annotation markup is interpretable by everyone. For legal and business documents, use stamps to indicate review status: REVIEWED BY (with reviewer name and date), APPROVED, or NEEDS REVISION. These stamps create a visual status record that is immediately recognizable when the document is opened. Comments can provide the detailed reasoning behind the status. When you receive an annotated document from multiple reviewers, consolidate all annotations into a single document by importing comment data or merging PDFs with their annotations preserved. Review each comment systematically: resolve it by making the requested change, or reply to explain why the change was not made. Tracking the resolution of every annotation is important in formal review processes. After the review cycle is complete and all annotations are resolved, flatten the document before final distribution if you do not want recipients to see the review history. Flattening merges annotations into the page content as visual elements — they remain visible but can no longer be selected, expanded, or deleted as separate annotation objects.

1. 1Establish annotation conventions (colors, types, meaning) before starting a multi-reviewer process.
2. 2Assign each reviewer a specific color or annotator name for easy tracking.
3. 3Track and resolve each annotation systematically before finalizing the document.
4. 4Flatten the PDF to remove interactive annotation objects before final distribution.

Beyond individual annotations, document-level marking is often needed for status communication. A DRAFT watermark across all pages communicates clearly that the document has not been finalized. A CONFIDENTIAL stamp on every page provides notice of sensitivity. A COPY watermark on a duplicate document distinguishes it from the original. LazyPDF's Watermark tool adds text watermarks to PDF pages programmatically — ideal for adding consistent document status indicators across all pages of a document. Unlike manual stamp annotations (which must be applied page by page), a watermark tool applies the marking uniformly across the entire document in one operation. For documents in active review cycles, a DRAFT watermark is standard practice. Once the review is complete and the document is approved, the workflow typically involves producing a clean final version without the draft watermark for official distribution. Keep the annotated draft version for your records and distribute the clean approved version to external recipients. Converting the annotated PDF to Word format is useful when reviewers' annotations have been resolved and you need to incorporate the changes into an editable document for the next revision cycle. LazyPDF's PDF to Word tool extracts the text content, allowing you to update the document in Word and generate a new clean PDF for the next review round.