The DynamicPDF™ Merger v3.0 for COM/ActiveX class library is designed to efficiently import, merge, form-fill and stamp pre existing PDF documents. It can import PDF documents from the file system . The resulting PDF document can then have content added to it and can be output to IIS Stream object, Byte Array,  or directly to a file on the file system. The assembly is written using 100% managed code and is accessible from language like VBScript. The generated PDF documents are 100% compatible with PDF version 1.4 and 1.5 and comply with the PDF specification as published by Adobe.

Further Reading

Getting Started
Topics on getting started with Merger for COM/ActiveX.
Programming With Merger v3.0 for COM/ActiveX
Introduces how to program with Merger for COM/ActiveX.

See Also 

Getting Started | Programming with Merger for COM/ActiveX