It has been possible to embed files in PDF output in InterFormNG for a while, but the same feature is now also implemented in InterForm400. As usual the new features/modules are officially released with the 2013 version to be released in early April, but it is possible to get your hands on a beta version, which can do this already now.
I have created a shock wave movie introducing this new module and placed it on our download site. You can download the movie here: http://download.interform400.com/shares/public/InterForm400_Embed_Definition_Demo.zip
The linked file also contains the resources that I used for the demo, the result and preliminary documentation, which will be a part of the new 2013 manual.
Please notice, that export/import of embed definitions has not been implemented in the current version.
To run the embed function you should install InterForm400 version 2012M506 (beta) or newer.
The 2012M506 version can be downloaded via this link: http://download.interform400.com/shares/ZipA/IF2012.M506.zip
Feel free to contact me if you have any questions about this.