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Comment & review
Read, highlight and reply. Free, no sign-up.
How to comment on and review a PDF
A reviewing view for reading closely and leaving comments others can reply to.
- Open your PDF. Comments from previous reviewers are shown.
- Comment and reply. Threaded notes anchored to the page.
- Download. Comments are saved into the PDF.
What a comment is once it is saved
A saved comment is standard PDF markup, not a Folia format. A thread anchored to text becomes a highlight annotation carrying one quad per line your selection covered, with your note as its contents, your name, the creation and modification times, and the words it refers to stored as the annotation's subject. Each reply is a separate sticky-note annotation pointing back to the root, and replies are put back in date order when the file is reopened. Acrobat, Preview, Edge and Chrome list them in their own comment panes and can reply to them, which is the whole point of saving a review this way rather than exporting it to a separate document.
Resolving a thread writes two things: a Folia key, so it reopens as resolved here, and the standard Review/Completed state other readers understand, so a colleague sees the discussion as finished rather than open. A thread you delete before saving is simply never written into the file.
Passing the file round a review cycle
Open a PDF that already carries comments — yours from last week, or a colleague's made in Acrobat — and they are read back in and counted, so a review continues instead of starting again. Saving rewrites the whole set from what is on screen: the previous generation of comment annotations is removed first, so a file that goes round three times does not come back with three copies of every note. Anything that is not a comment — links, form fields, stamps, ink, text boxes, and a bare highlight nobody attached a note to — is left exactly as it was.
Two limits, stated plainly. The PDF library keeps the superseded annotation objects in the saved file even after they are dropped from the page, so each round leaves a little unreferenced weight behind; nothing is lost or duplicated, but a heavily re-reviewed document ends up larger than it needs to be. And only highlight-shaped and sticky-note-shaped markup comes back as a thread you can reply to — a free-text box or an ink scribble drawn in another app survives untouched, but never appears in the comment list here.
Questions
Can several people review at once?
Not simultaneously — this tool is fully offline in your browser, so there is no shared server session. Pass the annotated PDF along and each reviewer’s comments accumulate in the file.
Whose name appears on my comments?
"You". There is no account here and nothing asks who you are, so that is what every note you write is signed with. Comments made by other people keep their own author names and dates when the file is reopened. Folia for Desktop has a reviewer name in its settings that goes on your comments instead.
Can I comment on a scanned PDF?
Only after OCR. A new comment starts from a text selection — you select the words, then click Comment on selection — and a scan has nothing to select. Run OCR PDF on it first. Pinned notes made in other apps still open here and can be replied to.
How do I delete a comment, mine or someone else's?
Select the thread, delete it, then save. The save rewrites the comment set from what is on screen, so a deleted thread does not reappear on the next round. Everything in the file that is not a comment is left where it is.
Are my files uploaded to a server?
No. Every tool on this site runs inside your browser, using the same engine as the Folia desktop app. Your file is read from your disk into your browser’s memory, processed there, and handed back as a download. It never crosses the internet, so there is nothing for us to store, leak or hand over.
Is there a file size limit?
We impose none. The only ceiling is your own device’s memory, which differs from one computer to another — so we read what your browser reports about this machine and show the resulting limit on the page. Light tools like merge and rotate handle far more than heavy ones like OCR, which must render every page. For anything larger, Folia for Desktop has no limit at all.
Is it really free? Do I need an account?
Yes, and no. Every tool is free and unlimited, with no watermark and no sign-up. Ads pay for the site, and your own computer does the work, which costs us nothing. Signing in with a paid Folia plan simply removes the ads.