You've been sent a PDF and it asks for a password before opening. That's an encrypted PDF — scrambled in a way that only the right password can unlock. It's the digital equivalent of a locked envelope.
How encryption works
When a PDF is encrypted, its contents are mathematically scrambled using a key derived from a password. Without the password, the file is just gibberish — even if someone intercepts it in transit or grabs it off a lost laptop. Modern PDFs use AES-256, the same encryption standard banks and governments rely on, so it's genuinely secure when used properly.
Two types of password
PDFs can have an open password (needed just to view the file) and a permissions password (needed to edit, print or copy). You can set either or both. With Flint you can protect a PDF with whichever level you need, and if you've forgotten the password but own the file, unlock a PDF gets you back in.
When to encrypt
Use encryption for anything sensitive: payslips, medical reports, contracts with personal details, ID documents. Don't bother for newsletters or marketing flyers. And remember — a password is only as strong as it is unguessable, so use something long and unique, not 'password123' or your dog's name.
FAQ
Can encryption be cracked?
AES-256 (the modern PDF standard) is effectively unbreakable with current technology if you use a strong password. Weak passwords, though, are guessable in minutes. The encryption is only as good as the password protecting it.
How do I share the password safely?
Send the PDF and the password through different channels. For example, email the file but text the password. That way, intercepting one doesn't give an attacker both.
What if I forget the password?
If it's your own file and you remember roughly what you used, Flint's unlock tool can help. If you've genuinely lost it, recovery is often impossible — that's the trade-off for real security.
Got something sensitive to send? Encrypt it in Flint and the file stays useless to anyone without the password.