PDF Editor
Edit PDF files for free. Fill & sign PDF. Add text, links, images and shapes. Edit existing PDF text. Annotate PDF
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Highlight, underline, strike out, comment and draw on a PDF, then download the marked-up file.
Annotate PDF opens your file with the Highlight tool selected, so you can mark passages the moment the page appears. Switch to Underline, Strikethrough, Comment, Freehand Highlight or Free Draw for other marks, add arrows and boxes, then save. It is free, needs no account and deletes the file within two hours.
Step by step
Drag the PDF into the drop zone or click Choose a PDF to annotate. The pages load in the editor with the Highlight tool already selected.
Drag across the words you want to mark. Open the Annotate menu to switch between Highlight, Underline and Strikethrough whenever a passage needs a different kind of mark.
Choose Comment to pin a note to a spot on the page, or Freehand Highlight and Free Draw to mark by hand. Shapes adds a Rectangle, Ellipse, Line or Arrow to point at a detail.
Click Save to write your marks into the PDF and download it. Undo and Redo let you take back a stray mark before saving.
Features
Highlight, Underline and Strikethrough snap to the text you drag across, so a marked clause lines up neatly with the sentence instead of floating as a loose box over it.
Comment adds a sticky note to any point on a page for a reviewer to read. Freehand Highlight and Free Draw follow a mouse, pen or finger for circling figures and adding quick sketches.
The Shapes menu adds a Rectangle, Ellipse, Line or Arrow, which is useful for pointing at a logo, a table cell or a misplaced image on a layout proof.
Annotations are marks laid over the page rather than changes to its text. Highlight, Underline and Strikethrough follow the words you drag across, Comment pins a note to a spot, and Freehand Highlight and Free Draw follow your pointer or finger. Shapes add a Rectangle, Ellipse, Line or Arrow. On save the marks are written into the PDF, and the original text and images underneath stay as they were.
Review work on a PDF usually means three kinds of mark: something to keep, something to cut and something to explain. Highlight covers the first, Strikethrough the second and Comment the third. Because this page opens with Highlight selected, a reader going through a long report can start marking passages as soon as the first page appears, then switch tools from the Annotate menu when a note or a deletion is needed.
Drawn marks help where words fail. Freehand Highlight works like a marker pen across a chart or a handwritten scan whose text cannot be selected, and Free Draw is for circles, ticks and margin sketches. On a design proof, an Arrow or a Rectangle points at the exact element to change. If you need to change the wording itself rather than comment on it, Add Text to PDF and PDF Editor open the same editor with text tools first.
Once the review is done, the marked-up file often moves on. Flatten PDF merges annotations into the page so they cannot be moved or deleted, and Remove Annotations strips them again when you need a clean copy of the original. Compress PDF shrinks the result before you email it.
Saving happens on our servers: the file is handled automatically with no human access and deleted within 2 hours. Annotating is free with no account and no limit on the number of files, and each PDF can be up to 200 MB.
Compared
Last checked 22 October 2026. Competitor facts come from their public pages on that date; prices and limits change, so confirm before you decide.
| Feature | Siliph | Adobe Acrobat online | Smallpdf | iLovePDF |
|---|---|---|---|---|
| Price for this tool | Free, every tool, unlimited tasks | Free online tools; Acrobat Standard $14.99 per month (annual plan) | About 2 free tasks per day; Pro about $15 per month (about $9 billed yearly) | Free with per-tool limits; Premium 500 INR per month (242 INR billed yearly) |
| Free file size limit | 200 MB per file, 2000 pages | Not stated on the page we checked | Not stated on the page we checked | 15–200 MB depending on the tool (4 GB on Premium) |
| Files per task on the free tier | Up to 50 files per task | Not stated on the page we checked | Not stated on the page we checked | Set per tool (merge 25, compress 2, PDF to Word 1) |
| Account required | No account needed | Sign in to save or share the result | Not stated on the page we checked | Not stated on the page we checked |
| Where files are processed and when they are deleted | Encrypted upload, deleted within 2 hours | Cloud processing; deletion window not stated on the page we checked | Cloud processing; files deleted after 1 hour | Cloud processing; deletion window not stated on the page we checked |
| Watermark on output | None | Not stated on the page we checked | Not stated on the page we checked | Not stated on the page we checked |
The Annotate menu has Highlight, Underline, Strikethrough, Comment, Freehand Highlight and Free Draw. The Shapes menu adds a Rectangle, Ellipse, Line or Arrow. The page opens with Highlight selected.
A scan has no selectable text, so text highlights cannot snap to the words. Use Freehand Highlight to drag a marker over the area instead, or run OCR PDF first so the text becomes selectable.
Yes. When you save, the marks are written into the PDF, so they appear in Acrobat, Preview, Chrome and other viewers. Comments show as notes that the reader can open.
No. Highlights, underlines, strikethroughs, comments and drawings sit on top of the page. The text and images underneath are unchanged, which is why the marks can be removed later.
Yes. Undo removes the last mark and Redo restores it, for as many steps as you need until you save. You can also select a mark and delete it on its own.
Yes. You can mark up as many PDFs as you like without signing up, each up to 200 MB, and the copy that reaches our servers is deleted within 2 hours.
Add Annotate PDF to your blog or website for free. The attribution snippet includes a link back to Siliph.
Embed code (iframe)
<iframe src="https://siliph.com/annotate-pdf/?embed=1" title="Annotate PDF — Siliph" width="100%" height="620" style="border:0;border-radius:12px;max-width:900px;" loading="lazy" allow="clipboard-write"></iframe> <p style="font-size:12px;color:#666;margin-top:8px;"><a href="https://siliph.com/annotate-pdf/" title="Annotate PDF — Siliph">Annotate PDF</a> powered by <a href="https://siliph.com/" title="Siliph — Free PDF Tools">Siliph</a></p>
Link for blog posts and tool lists
<p style="font-size:12px;color:#666;margin-top:8px;"><a href="https://siliph.com/annotate-pdf/" title="Annotate PDF — Siliph">Annotate PDF</a> powered by <a href="https://siliph.com/" title="Siliph — Free PDF Tools">Siliph</a></p>
Direct link: https://siliph.com/annotate-pdf