Sending a contract to a client with confidential commercial terms. If the email is forwarded, the attachment shouldn't be readable without the password you only sent to the right person.
Password protection on PDFs is real encryption — not just a permission flag. The file is actually encrypted with the password as the key.
Set the password
Open the PDF in Flint's password protection tool. Set a strong password — at least 12 characters, mixed case and numbers.
There are two password types: "open password" (required to view) and "owner password" (required to remove restrictions). Use open password for sharing.
Send the password separately
Email the PDF. Send the password by a different channel — text message, phone call, separate email, in person.
Never put the password in the same email as the PDF. If the email is intercepted, both are exposed. Separate channels means an attacker needs both.
Manage the key
Tell the recipient how to open the file. "Open in Adobe, Preview, or Chrome. When prompted, enter the password I'll text you."
For recurring sharing, agree on a key delivery convention upfront. Some teams use shared password managers; others use separate secure channels.
FAQ
How strong is PDF password encryption?
Modern PDFs use AES-256 encryption. Without the password, brute-force attacks take many years. Weak passwords (short, dictionary words) are the actual vulnerability.
What if the recipient forgets the password?
Without the password, the file can't be opened. Send the password again through the secure channel — but never in the same place as the PDF.
Can I send the password by email?
Sometimes acceptable if it's a different email (not a reply to the email with the PDF). Better to use a different channel entirely.
Does the password protect against screenshots?
No. Once opened, the content is visible. Combine with recipient watermarking for traceability.
Password-protected sharing is real security — when you handle the password handoff right. Encrypt with Flint, send the password separately, and share confidently.