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I am looking to encrypt a PDF file with a password.

My question is two-fold:

  1. is there a good software to do that for Mac OSx? I saw Acrobat has commercial software for that, but I am looking (surprise...) for something free -- I want to make very limited use of it.

  2. is the encryption (with password) relatively safe, and is okay to send personal identifying details with, assuming an eavesdropper doesn't know the password? Or are there crackers that can crack such PDFs relatively easy?

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There is indeed software that exists, considering Adobe's Acrobat software, has this capability. In order to determine if the encryption is "safe" you have to narrow down your requirements. The following support article explains what Acrobat supports.…. As for a free alternative to Acrobat, that would be a product recomendation, which is not on topic here at Superuser. You should be able to find and analyze the alternatives and determine if a free solution exists that meets your requirements. – Ramhound Dec 6 '13 at 14:10
At the very least you want a product that will encrypt the contents and metadata. Anything before PDF 1.6 is not as secure because previous to the PDF 1.6 version the file format does not have the capability to use AES encryption. – Ramhound Dec 6 '13 at 14:12
The best thing to do would to be to put it in a true crypt volume, you could put it in a encrypted zip file if you do not want to put convenience first – HackToHell Dec 6 '13 at 15:25

My personal recommendation is to use a free program called TrueCrypt to encrypt the file. TrueCrypt works with OSx and is a trusted program to encrypt files/hard drives/etc.

You can then encrypt the PDF file with AES. Just remember to use a strong password as the key, or the encryption will be worthless. The file will be safe from an attacker assuming the key you use is strong and unknown by the attacker.

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TrueCrypt encrypts disks and partitions, not single files. – pbies Dec 6 '13 at 18:53

Another possibility is gpg. This is a well-known and trusted encryption program, which can do symmetric encryption (ie, you decrypt it using the password you encrypted it with) or asymmetric (ie, using public/private key pairs).

Homebrew can install gpg for you (brew install gpg). It's a bit of a pig to build from scratch on OS X, since it has a non-trivial list of dependencies.

There's a OS X GUI application called GPGSuite. It looks good, but I don't have any personal experience with it.

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I would use packing utilities with encryption option. Surely use long password then. Compression to .zip or .rar should be enough. PDF is not compressable though, but can be encrypted.

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