Annotate & highlight
Highlight, underline, comment and draw - as real annotations, not ink.
This tool runs entirely in your browser. Your file is never uploaded, and you can verify that in your browser's network tab. Verify it yourself: open your browser's network tab and watch. You will see one small request asking whether you have tasks left - a tool name and a hash, never the file.
What this does
The marks this tool adds are annotations, not drawings. A real highlight appears in a reader's comment list, carries your name, can be replied to, filtered and deleted; a yellow rectangle painted onto the page is ink for ever. Text markup snaps to the words underneath rather than to a rectangle you drew approximately over them.
Use it when a document is going back to whoever wrote it: marking the clause you disagree with, striking a sentence that should go, leaving a note beside a figure that looks wrong, or circling the part of a drawing that needs redoing.
How it works
- Drop the PDF onto this page and wait for it to render.
- Select words to highlight, underline, strike out or squiggly-underline them, or pick a shape, a note or the pen for freehand ink.
- Set the colour and opacity, and type the comment that goes with the mark if it needs one.
- Put your name in Author so the recipient's comment panel says who wrote what.
- Leave Turn the comments into ink off unless the marks must not be editable.
- Press Annotate and the download starts.
Text markup follows the text. The page's text runs are read first, so a sentence that wraps over two lines becomes one annotation with a quadrilateral for each line, not one wide box slanting across the paragraph. Those quadrilaterals are written in the order the specification asks for - upper-left, upper-right, lower-left, lower-right, which is neither clockwise nor anticlockwise - and getting it wrong is why highlights from some tools render as bow-ties in Acrobat.
Nine kinds of mark are available: highlight, underline, strikeout, squiggly underline, sticky note, square, circle, line and freehand ink. All are written with the print flag set, because a review comment that vanishes when the recipient prints the document is a comment they never read. Highlights default to 40 percent opacity so the words under them stay legible.
No appearance stream is written for these annotations, so each reader draws them from the annotation data using its own conventions: a highlight looks like an Acrobat highlight in Acrobat and like a Preview highlight in Preview, and the exact edge and shade differ slightly. In exchange, the marks stay editable data rather than becoming pixels.
Turning the comments into ink runs the same pass as Flatten PDF: each annotation's appearance stream is drawn onto the page and the annotation deleted. Only marks that carry such a stream can be drawn, and ones the reader synthesises do not, so flattening immediately after adding leaves them in place. Open the file once in a reader and save it - that writes the appearances - then flatten.
Nothing about the document is sent anywhere: the name you put in Author is written into the file you download and nowhere else.
What this tool cannot do
- Highlight, underline, strikeout and squiggly need a text layer to snap to. A scanned page has none, so run OCR PDF over it first, or mark it up with the shape and ink tools instead.
- The annotations carry no appearance stream, so each reader draws them itself and they can look slightly different between Acrobat, Preview and Chrome. Flattening cannot burn in a mark that the reader is drawing.
Questions people ask
- Are these real PDF comments or just drawings on the page?
- Real annotation objects. They appear in the comment panel of Acrobat, Preview, Foxit and most other readers, carry the author name and the comment text, and can be replied to, filtered or deleted by whoever receives them. Drawn marks - what Edit PDF produces - are part of the page and cannot be removed.
- Why does my highlight cover exactly the words and not the box I dragged?
- Because the page's text runs are read before the mark is written, so the highlight is built from the actual position of the words you selected. A sentence spanning three lines becomes three quadrilaterals in one annotation, which is why it wraps properly instead of covering the whitespace at the end of each line.
- What does turning the comments into ink do?
- It draws each annotation onto the page and deletes the annotation, so nobody downstream can move or remove the marks. Only annotations carrying their own appearance stream can be drawn, and the ones added here are rendered by the reader instead - so open and save the file once in a PDF reader, which writes the appearances, then run Flatten PDF.
- Will the recipient see my comments?
- In any reader that supports annotations, which is effectively all of them, browser viewers included. The marks are set to print, so they appear on paper too. A viewer that ignores annotations entirely would show the unmarked page, which is a reason to flatten when the marks must be unmissable.
- Does the document leave my device?
- No. It is rendered and rewritten inside your browser, and the only thing added to the file is what you typed: the marks, their comments and the author name you chose. Nothing is uploaded: open the network tab and the only request is the allowance check, which carries a tool name and a hash rather than the file or a word of what you wrote.