PDFBlackbox (.NET)

PDFBlackbox.NET is a comprehensive collection of managed components that help you encrypt, sign and compress PDF documents from your .NET Framework applications. Both symmetric and certificate-based (X.509) encryption and signing is supported.
PDFBlackbox supports full range of PDF security operations, including
* PDF standard password-based data encryption using MD5 + RC4/40 or RC4/128 algorithms;
* PDF certificate-based public key data encryption using RSA algorithm and PKCS#7 format;
* certificate-based data signing using SHA1 with RSA algorithms and PKCS#1 or PKCS#7 format;
* ZLib compression;
* stream-based processing, which lets you handle huge amounts of data without significant memory requirements;
* support for PDF format versions 1.3 to 1.6
PDFBlackbox components are a clean-room implementation of PDF format specification, which don't use any third-party libraries for core functionality.
This is .NET edition, which can be integrated into Visual Studio 2003, Visual Studio 2005 , Borland Delphi 8 and Delphi 2005-2006 /.NET, C#Builder. It requires .NET Framework 1.1 or 2.0