Annotate a PDF Online: Highlight + Draw, Saved Into the File

You got a contract draft and you want to mark up the parts you have questions about. You’re studying a long PDF and you want to highlight what to remember. You’re reviewing a colleague’s document and you want to circle a typo. The job is markup — visible, durable, no fancy review workflow needed. The frustrating versions of this involve installing a desktop tool with a learning curve, or using a “free” online annotator that asks you to upload your PDF first.

Signegy annotates PDFs in your browser. Drag to highlight, click and draw to mark up freehand, save. The annotations are baked into the PDF as proper shapes, so they show up in every reader. Nothing uploads.

How It Works

1. Drop your PDF onto the tool above. The first page renders at editing scale; navigate with Prev / Next in the toolbar.
2. Pick a tool. “Highlight” lets you drag rectangles for a translucent yellow highlight. “Draw” lets you freehand draw red strokes. Switch tools as often as you need; both work on the same page.
3. Save. Click “Download annotated” and the new PDF saves with all annotations baked in. The file name follows [original]-annotated.pdf.

The interface is single-page-at-a-time on purpose — annotation is a focus task, not a multi-page browse task. Use the page navigation in the toolbar to move; annotations from previous pages stay saved.

Highlight vs. Draw

Highlight is a click-and-drag rectangle filled with translucent yellow (the universal highlighter color). It’s for marking text or sections you want to draw attention to. Drag from one corner of the area to the opposite; release to commit. The minimum size is small enough to highlight a single word, large enough to highlight a whole paragraph in one stroke.

Draw is freehand line drawing. Click and hold, move the cursor (or finger / stylus) to trace a path; release to commit. Useful for circling, underlining specific words, drawing arrows, or sketching a quick correction. The stroke is red so it stands out against the page content.

You can mix freely. A common workflow: highlight the whole paragraph in question with one rectangle, then draw a circle around the specific phrase that’s the problem.

Why Annotations Are Baked Into the PDF

Some annotation tools store annotations as a separate layer (PDF Annotation objects) that lives alongside the page content. The advantage: the original page is untouched, annotations can be edited or deleted later. The disadvantage: not every PDF reader displays them. A reader that doesn’t support the annotation layer will show the original PDF without any of your highlights or drawings.

Signegy bakes annotations directly into the page — the highlight is a translucent rectangle drawn onto the page; the drawing is a series of line segments drawn onto the page. They’re part of the page content, not a layer above it. Every PDF reader that can render a rectangle and a line can display them, which is every PDF reader.

The trade-off is that you can’t edit them after saving. For a “mark up and send” workflow that’s fine — once you save, you’re done. For a long review process where you want to add and remove annotations over time, a layered annotation tool is a better fit.

Use Cases

The three big ones: contract review, study notes, and quick corrections.

For contract review, you mark the clauses you have questions about, circle terms you don’t understand, and send the marked-up PDF back to your counterparty or your lawyer. Faster than writing a list of “see page 3, paragraph 2, second sentence” for every concern.

For study notes, you highlight the key passages in a textbook chapter or research paper. The marked-up PDF lives on your machine; when you come back to study, the highlights remind you what mattered. The browser-only architecture means you don’t need a study app or a sync service — just the file.

For corrections, you draw quick marks on a draft (typo, missing comma, “delete this paragraph”) and send the marked PDF back to the author. Faster than tracked changes if all you need is a few visible flags.

When You Want a Richer Editor

Three cases where Signegy’s annotator isn’t the right tool:

Comment threads with multiple reviewers. If two or more people need to add comments, reply to each other, and resolve threads, you need a tool with comment metadata and reviewer attribution — Adobe Acrobat, PDF Studio, or a dedicated review platform. Signegy’s annotations are anonymous shapes, not threaded discussions.

Text annotations with searchable text. If you want to type a sticky note or callout label that’s later searchable as text, this v1 doesn’t have a text tool yet. Coming.

Editing existing annotations. If someone sent you a PDF with their annotations and you want to modify or delete them, Signegy treats those as part of the page content (because they probably are, after a previous save). It can’t selectively edit them. Use Acrobat or a dedicated annotation editor.

What’s on the Roadmap (For Honesty)

V1 ships with: highlight rectangle, freehand draw, page navigation, undo, clear-page, and the bake-on-save flow. Not in v1: text labels / sticky notes, color picker, eraser, shape primitives (lines, arrows, ellipses), per-annotation edit after placement. These are planned but not promised on a date.

Pair With the Toolkit

Annotation often follows other steps — extract the section you want to mark up, annotate just those pages, then optionally merge them back with the rest of the document. Or annotate first, then sign the marked-up doc and send it back as your formal response. All in the browser, all with the same no-upload guarantee.

For forms specifically, annotating works as a fallback for PDFs that don’t have detected form fields — type-style fields can be drawn in by hand or, for v1, replaced with the visual mark.