PDF Annotator Tool
AIfreeforever's PDF Annotator tool helps you mark up and comment on your PDF documents right in your browser, with no software installs or accounts needed. After uploading your file, you can highlight text, add underlines, draw strikethrough lines, or insert notes and shapes like rectangles and arrows. All ten annotation modes work within a single workspace and process your files locally using the pdf-lib library, ensuring your data stays on your device. Once finished, download the annotated file as a standard PDF that works with any viewer or printer.
Highlight
Mark important areas with colored overlays and adjustable opacity for clear visual emphasis on any page.
Underline & Strikethrough
Add underline or strikethrough annotations with customizable color and stroke width to mark text precisely.
Text & Sticky Notes
Place inline text comments or sticky note boxes anywhere on the page for feedback and review.
Freehand Drawing
Draw freely on PDF pages using your mouse or touchpad with adjustable pen color and thickness.
Shapes
Place rectangles, circles, lines, and arrows to highlight specific sections or point to content.
Online PDF Annotator with Highlight and Markup Tools
Marking up PDFs is a core part of document review, whether you're flagging errors, leaving feedback, or highlighting key contract terms. The highlight tool allows you to place a colored overlay on any section with full control over color and transparency. If you need more precise edits, use the underline tool to add a colored line beneath your selection or the strikethrough tool to draw a line through the center for deletions. Every mode works independently, giving you the freedom to mix and match markup styles on any page.
Adjustable Colors, Opacity, and Stroke Width
Every tool comes with a dedicated color picker so you can choose the perfect shade for your annotations. When using highlight mode, an opacity slider lets you create anything from subtle overlays to bold, opaque markers. You can also adjust the stroke width for the underline, strikethrough, and freehand drawing tools from 1 to 8 pixels to achieve the exact line thickness your document requires.
Text Notes and Sticky Notes for Comments
Text notes and sticky notes simplify the process of leaving detailed comments on your files. Type your message in the sidebar and click anywhere on the page to place your note exactly where it's needed. Text notes embed your words directly into the document content, while sticky notes appear as small yellow boxes that mimic physical notes. Once you apply your changes, both types become a permanent part of the PDF structure.
Draw Freehand and Place Shapes on PDF Pages
Freehand drawing and geometric shapes offer visual markup options that go beyond simple text annotations. Mouse movements are tracked by the freehand tool and converted into line segments embedded directly in the file. You can use rectangles and circles to frame important content without obscuring it, while lines and arrows help you point out specific details during reviews or presentations.
Rectangles, Circles, Lines, and Arrows
Simply click and drag your cursor across the page to use any of the shape tools. Rectangles and circles appear as outlines, ensuring the text underneath remains visible, while lines and arrows help connect points or direct attention to specific areas. The color and stroke width settings you choose apply to all shapes, ensuring your visual markup stays consistent throughout the entire document.
Freehand Sketching for Quick Markup
Experience a natural way to draw by using freehand mode, which captures your cursor movements as you drag them across the page. Adjust the stroke width for fine or bold marks and select different colors to help organize your feedback. When you click apply, your drawings are instantly converted into permanent line segments within the PDF file structure.
Free PDF Annotator for Reviewers, Students, and Teams
Students preparing materials and professionals reviewing contracts will find comprehensive annotation tools here at no cost. Every mode is available the moment you start, with no requirements for accounts, watermarks, or limits on file size. Your sensitive documents remain secure on your own machine because the entire process runs locally in your browser. Once the tab is closed, all your data is permanently removed from memory.
No Signup, No Watermarks, No Limits
Access every feature as soon as you open the page, without having to worry about premium tiers, trials, or usage quotas. Your annotated PDFs download in their original quality without any added watermarks or platform branding. Because your session data only exists in your browser's memory, it disappears the moment you close the tab or leave the site.
Client-Side Processing for Document Security
Your files and notes never reach a server or travel across the network because all annotation tasks happen directly within your browser. This local processing makes it safe to handle confidential contracts, medical records, or legal documents that require strict privacy. You can work with complete confidence knowing your data is never exposed or stored externally.
Related PDF Tools
These tools complement your PDF annotation workflow:
- Edit PDF -- add text, images, signatures, rotate, delete, and reorder PDF pages
- Sign PDF -- draw, type, or upload a signature onto your PDF document
- Compress PDF -- reduce PDF file size for easier sharing and storage
- Merge PDF -- combine multiple PDF files into a single document
- Split PDF -- separate a PDF into individual pages or smaller files
- Convert PDF -- convert PDFs to and from other file formats
- PDF Reader -- view and read PDF documents online in your browser