Mark up any PDF in seconds. Draw highlights and boxes straight onto the page, then download the annotated PDF — free, secure, and entirely in your browser.
Yes. You can annotate and highlight PDFs online for free — no account, email, or credit card required. Sign up only if you want higher limits, larger files, or API access.
You can drag highlight bands over text and draw rectangular boxes around anything you want to call out. Marks are applied to the exact spot you draw on each page.
Yes. Your PDF is rendered locally in your browser, and when you process it the upload travels over an encrypted HTTPS connection and is deleted automatically within a few hours. We never share or sell your documents.
No. PDF4 works entirely in your web browser, so there is nothing to download or install. It runs on Windows, macOS, Linux, Android, and iOS.