I have extensive experience of working in Visual Studio .NET 2005 & Visual Studio .NET 2008.
This will be a windows application which will have two inputs as follows:
1. File input for pdf file
2. File input for text file (the file to be attached)
There will be a button, which upon clicking will ask for location to save the output pdf file with txt file embedded. After processing, the output pdf file (with the txt file embedded in page and position as specified by the user) will be stored in the specified location.
I will deliver the code in VB .NET 2008. Along with the code, I could also provide you an installable if required, which will be ready to install & run. The code will surely work in WinXP & Win 8.