Highlight and comment on a PDF for review, and hand back clear feedback

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Highlight PDFHighlight, underline, strike, notes. Free, runs on your device.Open

The review kit

The editor has 2 tools for review, and the first has 4 kinds of mark:

Tool	Key	What it makes	Starts in
Mark: Highlight	H	A wash of colour behind the words	Yellow
Mark: Underline	H, then Underline	A line under the words	Blue
Mark: Strike	H, then Strike	A line through the words	Red
Mark: Squiggle	H, then Squiggle	A wavy line under the words	Green
Note	N	An icon with your comment inside	Yellow

All 5 are standard PDF annotations. Each mark can take any of the 8 colours in the options bar, chosen before you drag, or afterwards by selecting the mark.

Review a lease, clause by clause

Our lease test document is the example: a tenant, Jana Čermák, wants to send her questions back to the landlord before signing.

1. Open the file at /highlight-pdf. The editor opens with the Mark tool in hand and Highlight chosen.
2. Read, and mark as you go. Drag from the first word to the last of each passage. The words that will be marked light up while you drag, line by line, so a mark never catches half a line by accident. Let go and it is placed.
3. Switch the kind of mark in the options bar when the concern changes: Underline for a date to confirm, Strike for a clause she wants removed, Squiggle for wording that is unclear.
4. Say why, in a note. Press N, click in the margin next to the mark, type “Clause 4: start date conflicts with clause 9”, press Enter. Press H to go back to marking.
5. Fix mistakes as they happen: Ctrl+Z undoes the last mark, and with the Select tool (V) a click on any mark shows its colour and Delete.
6. Add the key on page 1: one note that says what the colours mean (next section).
7. Save with Ctrl+S, and send the file.

Every mark and note is a step in the Changes list on the right, with its page number, so before saving you can see at a glance which pages got a look.

A colour system that survives the handover

Marks are only useful if the author can read them without a phone call. One colour per concern does that:

Colour and mark	Means
Yellow highlight	Agreed, important, keep
Red strike	Proposed for removal
Blue underline	A date or an amount to confirm
Green squiggle	Wording that is unclear
Orange note	A question that needs an answer

Write the key into the first note on page 1, for example “Review by Jana Čermák, 11 October 2026. Yellow: agreed. Red strike: please remove. Blue: please confirm. Green: unclear wording. Orange notes: questions.” getPDF does not stamp an author name or a date on marks and notes, so this first note is also where the reviewer’s name lives.

If the file may be printed in black and white, rely on the kind of mark more than on its colour: a strike, an underline and a squiggle stay distinct in grey, while a yellow and a green highlight do not.

How the comments travel

getPDF writes each mark as a standard PDF highlight, underline, strike-out or squiggly annotation, and each note as a standard text annotation. Each is saved with its drawn appearance and the flag that allows printing, so viewers that only draw what they are given still show it. Highlights are drawn so that the text shows through them, and the words underneath stay selectable and searchable.

They are small: on our invoice test file a highlight added 685 bytes and a note 1,242 bytes, so a review with 50 marks adds well under 100 KB.

Where the author will find them, per the apps’ own help pages (checked on 11 October 2026): Adobe Acrobat lists every mark and note in its Comments list in the right pane, and can filter it by type, author and status and print a comment summary; Apple’s Preview lists them under View, Highlights and Notes. Browser viewers draw the marks on the page; how they show a note’s text differs between browsers and versions, so an author who must answer every note is better off in an app with a comments list.

Highlighting a scanned page

A scan is a photo of a page, so there are no words for the Mark tool to find, and it says “There is no text there to mark. Drag across the words.” Two ways round it:

• Run OCR first. OCR PDF adds a layer of recognised text that looks exactly like the scan but can be selected; after that, highlights land on the words. Make a scanned PDF searchable covers it.
• Draw instead. Press S for the Shape tool, pick the rectangle and leave the fill empty, then drag a box around the passage. It is an outline, not a highlight, and it is part of the page rather than a comment, but on a scan it says “look here” just as well.

Do not use a filled rectangle as a highlight on a scan: the shapes have no transparency setting, so a filled box covers the ink.

Two ways to hand it back

The Save button’s menu offers 2 PDFs:

• Save PDF keeps every mark and note as an annotation: “Fields, marks and notes stay editable in any app.” This is the review copy. The author can reply, recolour, delete.
• Save flattened PDF draws the marks into the page: “nobody can change them”. Highlights, underlines and strikes look the same as before. Notes do not: flattening keeps a note’s icon and drops its text, which we confirmed on a test file. Flatten only after the discussion is over, and never a file whose notes still need reading.

The honest part: what review marks are and are not

Marks and notes are feedback, and they behave like it. They are visible to anyone who opens the file and removable by anyone with an editor; that is how the author clears them once dealt with.

They are not redaction. A highlight or a strike over a salary leaves the salary readable, selectable and searchable; a black rectangle drawn on top hides it from eyes only. If something must not be read, use Redact PDF, and see the privacy and protection guide for the rest of the file.

They are not a signature either. Agreeing to a reviewed contract is a separate step, covered in Sign and fill a PDF.

And getPDF is not a review platform. It has no reply threads, no author and date stamps, no resolved status, no comment export and no shared live session: it works on one copy, on one device. For a review with many people answering each other, Acrobat or a shared document tool fits better. For one reviewer handing back one marked-up file, without uploading a contract anywhere, this is the short path. For marks of one kind in depth, see Add notes and comments to a PDF and Cross out text in a PDF; for every other change, Edit a PDF.