Highlight, underline, or strikethrough text in your PDF documents.
Your file stays completely private. All annotation happens locally Γ’β¬β no uploads, no servers. Drag to draw highlights, underlines, or strikethroughs over text, then download the annotated PDF.
Free users limited to 10MB & 5s wait. Upgrade for 100MB & no limits
Add highlights, underlines, and strikethroughs to your PDF documents. Select an annotation mode, then click and drag over any text to mark it up. All annotations are drawn as colored rectangles and lines Γ’β¬β perfect for studying, reviewing documents, or marking up drafts.
Perfect for: highlighting key passages in research papers, underlining important clauses in contracts, strikethrough text in drafts, and reviewing PDF documents with visual annotations.
All processing happens locally in your browser Γ’β¬β no uploads, no servers, complete privacy. Keywords: annotate PDF online free, highlight PDF, underline PDF, strikethrough PDF, PDF annotation tool.
Marking up a PDF with highlights, underlines, and strikethroughs helps you study, review, and communicate feedback without touching the original text. This tool renders your document in the browser and lets you draw annotations directly over each page. The file never leaves your device, so even sensitive paperwork stays private while you work.
The tool offers three annotation modes. Highlight covers a section with a translucent yellow wash, ideal for pulling out key passages in research papers or reports. Underline draws a green line beneath the text you select, a natural fit for important clauses in contracts. Strikethrough draws a red line through content, which is useful when a draft needs to show what has been cut without erasing it.
Each annotation is applied by clicking and dragging over the area. The colored rectangles and lines are drawn onto the page exactly where you place them, so the result looks like a careful markup rather than a rough scribble. A live counter tracks how many annotations you have made across the whole document.
The page renders right in the tool, and you move between pages with the previous and next buttons. There is no upload step beyond selecting the file, no conversion, and no separate viewer to juggle. If you misplace a mark, Undo Last removes the most recent one on the current page without disturbing anything else.
The preview updates as you draw, so you see the finished look before you save. Once you are happy with the marks, a single button applies everything and downloads the annotated PDF. The whole loop, from selecting the file to saving the result, stays inside one browser tab.
The annotation count updates as you work, so you always know how many marks have been applied before you download. The output is a standard PDF that opens in any reader, on any device, with the marks visible exactly where you drew them.
Pro tip
Underline and strikethrough look best when you drag precisely along a line of text rather than a tall block. For dense pages, zooming in on your browser before dragging gives you finer control over placement, and you can mix modes freely across a single page.
Students use highlights to revisit study material before exams, reviewers mark drafts before sending feedback, and teams flag contract clauses for discussion. Because the tool runs client-side, you can annotate confidential research or client documents without uploading them anywhere. Free usage supports files up to 10MB with a brief wait, while Premium accepts up to 100MB with no waiting period.
Few people annotate a document correctly in one sweep. A common approach is to highlight the passages worth keeping on a first read, add underlines where something deserves emphasis on a second pass, and reserve strikethrough for the sections you decide to cut. Working this way keeps each mode meaningful instead of turning the page into a wall of color.
The undo button makes that process low risk. A misplaced line or an overzealous highlight disappears with one click, and because every page keeps its own list of marks, nothing you did elsewhere is affected. The mode buttons sit at the top of the page, so switching between them takes a single click.
Annotated PDFs are convenient for exactly this kind of back-and-forth: one file holds both the original content and your marks, so nothing gets lost between versions. Hand the file to a colleague and the highlights travel with it, no separate notes file required. What you drew in the browser is exactly what they see.