How to send a PDF securely by email
Updated
Sending a payslip to a landlord, a passport scan to an agency or a signed contract to a client usually means email. Email is convenient, but an attachment can end up in the wrong inbox, be forwarded, or sit in mailboxes for years. A few minutes of preparation makes a big difference. This guide gives you a simple routine to follow before you hit Send.
What can go wrong
It is rarely a sophisticated attack. The common problems are ordinary:
- The wrong recipient. Email apps suggest addresses as you type, and it’s easy to pick the wrong “Sam”.
- Forwarding. Once sent, the file can be passed on to anyone.
- Old mailboxes. Attachments stay in your Sent folder and the recipient’s inbox, sometimes for years. If either account is broken into later, the file is there to find.
- Too much information. A whole statement is sent when only the first page was needed.
The routine, in order
The order matters. PDFHive’s tools can’t change a protected PDF, so the password always goes on last.
1. Send only what’s needed
If the recipient needs proof of address, they probably need the first page of a statement, not all twelve. Remove the rest with Delete PDF pages. Deleted pages really leave the file, so their contents can’t be recovered from the copy you send.
A warning about black boxes: drawing a black rectangle over a number in a PDF app usually only hides it on screen. The text is often still underneath and can be copied out. Removing the whole page is safe. Hiding part of a page needs a proper redaction tool.
2. Mark who it’s for (optional)
For documents that might be passed around, such as ID copies, add a text watermark with Watermark PDF, for example “Copy for ABC Lettings, October 2026”. It doesn’t stop anyone forwarding the file, but it makes a copy less useful for anything else, and shows where it came from.
3. Make it small enough to send
Many email services won’t accept attachments over about 20-25 MB, and large files are slow to open on phones. Compress PDF for email brings it under 10 MB, which suits most inboxes.
4. Add a password, last
Open Protect PDF, type a password twice and click Protect PDF. The file is encrypted with AES-256, so it can’t be opened without the password. Choose a good one:
- Long beats complicated. Three or four unrelated words, such as “lamp-river-cactus-42”, are both strong and easy to read out.
- Never reuse a password from your email or bank.
- Use a new one for each recipient or document, so one shared password doesn’t unlock everything.
Keep your unprotected original somewhere safe. If you forget the password, nobody can open the protected copy.
Share the password separately
Sending the password in the same email defeats the point: anyone who gets the email gets both. Instead:
- Send it by text message or a messaging app, or tell the person by phone.
- Or agree on it in person before you send anything.
Write the email so it’s clear what’s coming, for example: “The attached PDF is password-protected. I’ll text you the password.”
What the recipient does
Nothing special. When they open the attachment in any modern PDF reader, including the ones built into Chrome, Edge, Safari, iPhone and Android, it asks for the password and then shows the document as normal.
If they need to keep an unprotected copy, for example to add it to their own records, they can remove the password with Unlock PDF, using the password you gave them. It’s worth telling them in your message whether you’d rather they kept it protected.
Before you press Send
- Check the recipient’s address letter by letter, especially if your email app filled it in.
- Open the protected PDF yourself and type the password, to make sure it works.
- Make sure you attached the protected copy, not the original.
When email isn’t the right tool
For very sensitive documents, or anything you need to be able to withdraw later, ask whether the organisation has its own secure upload portal. Many employers, banks and agencies do, and using it keeps your document out of mailboxes altogether.