Mark up a PDF the way you would on paper
Reading a document with a highlighter in hand is still one of the best ways to study or review. Annotate PDF brings that to your screen. Select a passage to highlight it, or highlight freehand over any area, such as part of a chart or a scanned page. Type free text anywhere on the page to leave a note, draw with your finger or mouse to circle a number or cross out a line, and insert an image or a stamp when you need to mark a page as reviewed.
Every mark has its own color and thickness, so you can use one color for questions and another for things to fix. Anything you add can be moved or deleted until you save.
Real annotations that other readers understand
Your marks are saved as standard PDF annotations, not burned into the page. That means they show up in Adobe Acrobat, Chrome, Edge and most PDF readers, and whoever receives the file can keep editing or removing them there. It is the behavior you want when a document is going back and forth for review: a colleague can delete a note once the issue is fixed.
If you would rather lock the marks in place so no one can change them, run the saved file through Flatten PDF. The annotations then become a fixed part of the page.
Everyday uses
Students highlight key ideas in readings and add short notes in the margin before an exam. Editors and teachers mark up drafts with circled errors and typed comments. People reviewing a lease or a service agreement highlight the clauses they want to ask about and send the file back with their notes. Designers stamp proofs to show which pages are approved.
Because the file stays a regular PDF, the recipient does not need any special program to see your work. You can also open the file in PDF Reader first to search for the passages you want to mark.
Limits worth knowing
There is no underline tool and no threaded comments, so you can’t reply to someone else’s note inside the file. Highlighting by selection needs a PDF with real text; on a scanned page, use freehand highlighting or run OCR PDF first. Annotations sit on top of the page and don’t change the original text. To add permanent text, images or shapes, Edit PDF is the better fit.
Password-protected PDFs need to be unlocked first with Unlock PDF.
Private and free
Annotating happens in your browser. The PDF never leaves your device, and nothing is stored on our side. ConvertirDocs is 100% free: no sign-up, no limit on how many files you annotate and no paid tier.