Sending a copy of your ID: watermark it and limit the damage if it leaks

Renting a flat, starting a job, opening an account, registering a SIM card, applying for a course: almost every one of these now involves sending someone a copy of your passport, citizenship certificate or national ID card. Once you press send, you have no control over that copy. It sits in an inbox, gets forwarded to a colleague, is saved to a shared drive and is rarely deleted.

You cannot stop that, but you can make the copy much less useful to anyone except the person you sent it to. That is what this guide is about.

First, ask what they actually need

The safest copy is the one you never send. Before you scan anything, it is worth asking a few questions.

• Do they need a copy, or just to see it? Many checks only require someone to look at the original document in person.
• Do they need both sides? If not, send only the side with the information they asked for.
• Do they need every detail? Some organisations accept a copy with irrelevant numbers partly covered. Others, such as banks doing identity checks required by law, need the full document. Ask rather than guess, because a copy they cannot accept means doing it all again.
• Is there a secure upload portal? A portal that deletes documents after verification is better than email, which keeps a copy on several servers indefinitely.

The watermark that actually helps

A watermark on an ID copy does one job: it ties that copy to a single purpose. If the image turns up somewhere it should not, it is obvious where it came from and that it was never meant for anything else. That makes it much harder to reuse the copy to open an account, rent a property or pass an identity check elsewhere, because the person checking can see it was made for someone else.

A useful watermark has three parts:

1. Who it is for. The name of the organisation receiving it.
2. What it is for. The specific purpose: a tenancy application, a job offer, a course enrolment.
3. The date. When you sent it.

For example: COPY FOR GREENFIELD LETTINGS - TENANCY APPLICATION - 03/10/2026. The word COPY on its own is almost useless, because it says nothing about where the copy should be.

Where to put it

Placement matters more than people expect. A watermark sitting in an empty margin can be cropped off in a few seconds, leaving a clean ID behind. The text has to cross the document itself.

• Run it diagonally across the card, so it passes over the photo and some of the printed details.
• Use a tiled watermark for a whole-page scan, so there is no clean corner to cut out.
• Make it stronger than a normal document watermark. On a contract, 15 to 20 per cent opacity is enough. An ID card is small and busy, so 25 to 35 per cent is usually needed for the text to stay readable once the image is shrunk or printed.
• Keep the important details readable. The recipient still has to check your name, number and photo. Test it: if you cannot read your own document number, they cannot either.

The Watermark PDF tool lets you set the text, angle, opacity and position, including a tiled pattern across the whole page.

Bake it into the image

This step is the one most guides miss. A text watermark added to a PDF is a separate text object sitting on top of the page. Anyone with a PDF editor can select it and press delete, and the clean scan underneath reappears.

To make the watermark permanent, flatten the page so the watermark becomes part of the pixels:

1. Make a PDF of your ID scan. If you have photos, use JPG to PDF.
2. Add the watermark with Watermark PDF.
3. Convert the watermarked PDF to an image with PDF to JPG at 200 or 300 DPI. The watermark is now part of the picture and cannot be lifted off.
4. Send that JPG, or turn it back into a PDF with JPG to PDF if the recipient wants a PDF.

Someone could still try to paint over the watermark in an image editor, but on a photo and printed text that is slow work and leaves visible damage. That is the point: you are not making misuse impossible, you are making it more effort than it is worth.

Hidden information in photos and PDFs

A photo straight from a phone camera often carries more than the picture. Its EXIF data can include the date, the phone model and, if location tagging is on, the GPS coordinates of where you took it, which for most people is their home. That is not something to attach to an identity document.

The flattening step above helps here too. An image produced by rendering a PDF page is a new picture, made by your browser, and does not carry the camera's EXIF data. The PDF itself has its own properties, such as title and author, which you can check and clear with PDF metadata.

Making a good copy in the first place

A blurry, glare-covered copy gets rejected and you end up sending a second one, so it is worth getting right first time. Lay the card flat on a dark, plain surface, in even daylight, and avoid flash, which bounces off laminated cards and hides the details. Hold the phone directly above it, not at an angle. There is more on this in how to scan a document with a phone camera.

A standard ID card is 85.6 by 54 millimetres, the same size as a bank card. At 300 DPI that is about 1,010 by 640 pixels, which is plenty for anyone to read. You do not need a 12-megapixel original, and a smaller file is easier to upload.

After you send it

Keep a short note of who you sent copies to, when, and for what. The date in the watermark makes this easy to match up later. If you ever hear about a data breach at an organisation on that list, you will know your document was involved and can take action, such as contacting the authority that issued it or watching your accounts more closely.

And delete the working files: the unwatermarked scan in your Downloads folder and the photo in your camera roll are copies too.

Every tool used in this guide runs in your browser. Your ID scan is processed on your own device and is never uploaded to this site.