1)   Encrypt PDF Command Line 2.3 Encrypt PDF software allows you to encrypt (using standard 40-bit or 128-bit supported by Acrobat Reader 5.0 and up) existing PDFs. 2)   Encrypt PDF (Secure PDF) 2.3 Encrypt PDF software allows you to encrypt (using standard 40-bit or 128-bit supported by Acrobat Reader 5.0 and up) existing PDFs. 3)   Encrypt PDF SDK-COM Component 2.1 Encrypt PDF SDK-COM allows you to encrypt (using standard 40-bit or 128-bit supported by Acrobat Reader 5.0 and up) existing PDFs.