Keep your PDFs safe from harm

Your PDF file protection will depend on the strength of your password. When thinking of how to password-protect a PDF, a good rule of thumb is to create passwords that are:

• At least 12 characters long
• Include a mix of upper and lowercase letters
• Include numbers and special symbols (e.g. ! or @)

As an extra measure to protect text and other PDF elements, you can also encrypt PDFs. PDF Extra supports the industry-standard RC4 (128 bit) and AES (up to 256 bit) ciphers.

If you're looking for a reliable PDF unlock method, the unfortunate reality is that you won't find one since it's not possible to remove security from a PDF without knowing the password beforehand. So, to unlock a PDF document, you would either have to be the owner of the document or contact the original owner to give you the correct password.

You're probably using the free version of PDF Extra, which doesn't have this feature included. For the best experience, consider upgrading to PDF Extra Premium or PDF Extra Ultimate to benefit from the full range of protection features - see our pricing plans.

A digital signature is a secure type of electronic signature that uses a digital certificate to authenticate the identity of the signer. It serves as a digital equivalent of a handwritten signature and guarantees that the document has not been modified since it was last signed. This type of signature is often used for legal documents, contracts, and other official paperwork.

To add a digital signature to a PDF, you need to have a digital signature certificate proving that you own the document. In case you don't have one, you can easily create a digital signature with a trusted Certificate Authority vendor and then import it into PDF Extra.

To encrypt PDF documents, access PDF Extra’s file protection settings and set a custom password, then choose the type of encryption cipher you want to use: 128-bit RC4, 128-bit AES, or 256-bit AES. For extra security, you can also check the mark to encrypt PDF metadata, then simply share your file as a regular or a zipped email attachment.

A digital signature acts as a seal on a letter that proves it hasn't been opened since it was sent. The sender has a special seal (private key) to close the letter and anyone can check if it's still sealed properly (with the sender's public key). A digital certificate, on the other hand, is like an ID badge that proves who the sender is. It's given by a trusted group (Certificate Authority) and helps you trust that the letter (PDF file) came from who it says it did.