From Guangming Software:
PDF Security ActiveX Component can encrypt PDF with standard 40-bit or 128-bit encryption. You can also set the permission of the user such as printing, modifying etc. You can make secure PDF and protect your PDF in one function call. PDF Security ActiveX also provides the ability to decrypt an encrypted PDF given the password. Add "encrypt pdf " or "decrypt pdf " feature to your application now! Both encryption and decryption are done by PDF Security ActiveX Component itself without the need of installing additional software such Acrobat PDF Reader.You can make secure PDF documents easily to achieve password enabled content protection. The features are: Encrypt and decrypt PDF files; Supports PDF user password and owner password protection; Password protect opening of the PDF document; Disable printing of the PDF document ; Disable copying of text/graphics ; Disable modifications to PDF the document ; Password protection for PDF files with 40 or 128 bit encryption ; Examples in VB, ASP, VB Script are provided.