Edit a PDF in Your Browser

Add a note, a date, a circle or an initial to a PDF before you fax it — in your browser, drawn on top so the document underneath is untouched.

This tool edits your PDF inside your own browser, so it needs JavaScript switched on.

  • Nothing is uploaded — not stored, not deleted later
  • The original stays intact — marks go on top
  • Free, no account, no watermark

Highlighting is the wrong tool for a fax

This is the one thing worth knowing before you mark anything up. A fax carries one bit per pixel — every dot is either black or white. A yellow highlight is a mid-tone, so the receiving machine has to decide which side of its cut-off it falls on, and on a lot of machines it lands on the dark side. Your emphasis arrives as a solid block over the words you were pointing at, which is the opposite of what you wanted.

Use the pen instead: underline the line, or draw a circle or a bracket beside it. A thin dark stroke survives the conversion intact because it is already the kind of mark a fax can carry. Highlighting is there because this file may not only be faxed — if you are emailing it as well, a highlight is the right mark and it will look correct on screen. Just do not rely on it reaching a fax machine the way you see it here.

What it does, and what it does not

Everything here is drawn on top of the page. Your text, images, pen strokes and blocks become new content layered over the document; the original page is copied through untouched, so its text stays selectable and any form fields still work. That is deliberate, and it is why the file stays small and searchable rather than becoming a flat picture of itself.

What it cannot do is change what is already there. You cannot retype a paragraph or correct a typo in the original — that requires rebuilding the page’s text and fonts, which is not something a browser can do honestly. If you need to cover a mistake and write over it, the white-out block plus a text box is the practical route. And if the document is a real fillable form, the form filler is the better tool, because it writes into the actual fields.

Questions people ask

Does the white-out actually remove what is underneath?
Not on its own. It covers the area with an opaque block, exactly like correction fluid on paper — but in the PDF the text underneath is still there and anyone can select it or pull it out with a text extractor. Faxing it is safe. A fax transmits a rasterised image of the page, so the covered text has nothing to travel in and the recipient genuinely cannot recover it. The exposure is the file on your own disk: if you might email that PDF instead of faxing it, run it through the fax optimizer first. That rewrites every page as a one-bit image and removes the text layer entirely, which is the honest way to make a cover-up permanent. Until you do that, treat the file as if the hidden text were visible.
Can I edit the text that is already in the PDF?
No. Changing existing text means rebuilding the page with its original fonts, spacing and layout, and no browser tool does that without visibly wrecking the document. What works in practice is covering the old text with a white-out block and typing the replacement over it. It is not elegant, but on something you are about to fax it is indistinguishable from the real thing.
Will my pen marks survive being faxed?
Yes, better than almost anything else you can add. A dark stroke on white paper is exactly what fax was built to carry, so an underline, a circle or an arrow comes through cleanly. Keep it reasonably thick — a hairline can thin out to nothing at standard resolution — and run the finished file through the fax optimizer to see the result before you send.
Does adding things make the file much bigger?
Text, pen strokes and blocks add almost nothing — they are drawing instructions, a few bytes each. An image is different: it goes in at whatever size you supplied, so a photo from a modern phone can add a couple of megabytes on its own. If that matters for an upload limit, shrink the image before you add it, or run the finished PDF through the optimizer afterwards.
Can I mark up more than one page?
Yes. Use the page arrows and add whatever you need on each one; everything is kept per page and saved together at the end. Each item can be dragged to reposition, nudged with the arrow keys for precision, or removed with Delete once selected.
Is my document uploaded anywhere?
No. Both the preview and the finished PDF are produced on your own device, so nothing is transmitted to us or anyone else and there is no server copy to delete afterwards. Load the page, disconnect from the internet, and it still works. That matters here more than usual, because marking up a document usually means you are annotating something private.

Then send it

Run the marked-up file through the fax optimizer and check the before-and-after — that is the step that shows you what your notes will actually look like at the other end. Then send it with anything you like. From a phone, Municorn Fax handles PDFs directly on iPhone and Android and includes one free test fax, which is worth spending on a single annotated page before you send the whole thing; after that it is $9.99 a week — see plans.

More on preparing documents

Optimize a PDF for fax

See what your marks look like in black and white.

Fill in a PDF form

If the document has real fields, use these instead.

Sign a PDF

Add a signature and place it on the page.

Faxing medical records

What HIPAA expects when patient records go by fax.

About Tamsin Gable

Head of PR at Municorn and a Forbes Communications Council member since 2025. Tamsin covers fax technology, secure document workflows, and how regulated industries handle sensitive communications.