Q:

Merging two PDF documents into one

Can I merge two or more PDFs in asp.net? I know I can do Word and Excel files using interop. But can I merge PDFs? 
Please suggest any suggestions or any links.

A:

Try iTextSharp:

iTextSharp is a C# port of iText, and open source Java library for
  PDF generation and manipulation. It can be used to create PDF
  documents from scratch, to convert XML to PDF (using the extra XFA
  Worker DLL), to fill out interactive PDF forms, to stamp new content
  on existing PDF documents, to split and merge existing PDF documents,
  and much more.

Here's an article on how to do it.

