Commenting on a PDF is easy. Every operating system and most browsers can do it for free, and the steps are below.
Collecting the comments is the part that goes wrong. Send one PDF to four people and you get four marked-up copies back, each missing what the others said, and somebody has to merge them by eye before a single change gets made. That is where the afternoon goes — not in the annotating.
This guide covers both: the tools first, then the merge.
The quickest free ways to mark up a PDF
Adobe Acrobat Reader (Windows, macOS — free)
The most complete of the free options, and the one your client most likely already has.
- Open the PDF in Acrobat Reader.
- Open the Comment tools from the right-hand pane or the toolbar.
- Pick a tool: a sticky note for a remark pinned to a spot, highlight for text, draw for anything freehand, or a text callout with a leader line pointing at what you mean.
- Type the comment. It is stamped with your name and the time.
- File → Save As, then send the saved copy back. The comments travel inside the PDF.
The comments pane lists every remark in order, which is what you want when you are working through them rather than reading them.
Preview (macOS — built in)
- Open the PDF, then click the Markup icon (a pen tip) in the toolbar.
- Use Note for a pinned comment, plus highlight, text and shape tools.
- Save. Comments and highlights are preserved in the file.
Fast for one or two remarks. It gets awkward once there are twenty, because Preview has no proper comment list to read them from.
A browser
Microsoft Edge's built-in PDF reader has highlight, draw and text tools and can save the annotated file — enough for a quick pass with nothing installed. Chrome's built-in viewer, at the time of writing, opens and prints PDFs but does not annotate them; you would need an extension or a web tool. Ours is one: annotate a PDF opens the file in the tab you are already in — arrows, boxes, text and highlights, saved back out as a PDF, free and with nothing uploaded.
Google Drive
Upload the PDF to Drive and open it in the preview: you can leave comments and reply to them, and everyone sees the same thread. This is genuinely the closest free thing to shared review — with two catches. The comments live in Drive rather than in the file, so they vanish when someone downloads it, and your client needs a Google account to take part.
On a phone
iOS opens a PDF from Files or Mail and offers Markup — pen, highlighter, text box, signature. Android does the same through Drive or a reader app. Worth knowing, because a proof sent to a busy client is opened on a phone far more often than anyone designing it expects.
The bit that actually costs you time
Every method above produces an annotated copy of the file. One person, one copy.
Send a proof to a customer, their colleague and whoever signs the invoice, and you receive three files back — assuming all three arrive. Their remarks overlap, two of them contradict, one arrives as an email sentence instead of an annotation, and none of them can see what the others said, so the same point comes back three times in three wordings.
Merging that is manual work, and it is dangerous work: it is where a comment gets dropped silently, and where somebody marks up the previous version because that was the attachment they still had open.
Three habits reduce it without buying anything:
Ask for one consolidated reply. Name a person on their side to collect their colleagues' remarks before sending. It moves the merge to the party who understands the intent behind it.
Make comments locatable. "The date on the back page, second line" is workable. "The date is wrong" starts a search. Ask for a page number and a position, every time.
Never let two versions be open at once. A new version means a new file name that has never been used, and a one-line note of what changed. The mechanics are in how to stop printing the wrong version.
Acrobat's shared-review features can merge comments from several returned copies, and if everyone in the chain has Acrobat and the patience to use it, that works. In production shops it usually is not true of the customer, which is why most feedback still arrives as an email with three bullet points and a screenshot.
When one shared link is the better answer
Read this knowing it describes our own product.
The alternative to sending a file is not sending it. Proofavo hosts the proof and gives you one link. Everybody who opens it sees the same artwork and the same comments, so nothing has to be merged afterwards.
- Comments are pins on the artwork. A click on the spot, then the remark — so "this is too close to the edge" arrives attached to the thing that is too close to the edge.
- No account for the person reviewing. No sign-up, no app, no password. They open the link on the phone they were already holding.
- Everyone sees each other's notes, which quietly kills the duplicate-remark problem before you have to sort it out.
- There is one current version. Nobody can comment on last week's file, because last week's file is not what the link shows.
- A comment has to be settled before the proof can be approved, so "approved, but…" cannot happen.
- The approval names the exact file, and produces a downloadable record with the version, the person, the time and a SHA-256 fingerprint — the audit trail an inbox does not give you.
You can try the whole loop, comments and approval, in the live demo. No sign-up, and the approval at the end produces a real record.
What it is not: a PDF editor. It will not let you change the artwork, and it is not a preflight check. It is where other people tell you what to change, and where they say yes.
For how this fits a print shop's day specifically, see proofing for print shops.