To lock access to its confidential documents, there are two solutions. The first is to make it unreadable files by encrypting their content. It is the role of cryptographic software. PGP remains the reference. But compression software such as WinZip and PKZIP are also able to encrypt the contents of archives. However an unreadable document places for sure the alarm bells about its value … unless you hide it in another document to innocuous appearances. An audio file or an image, for example. This second solution is proposed by the steganography software.
Invisible Secrets (freeware)
Steganos Security Suite (commercial)
Conceal documents as images and sounds.
PKZIP for Windows (freeware)
Compress and encrypt files.
PGP Personal (freeware)
The reference tool for encrypting documents.
Compress and protect the contents of archives.