How do you modify a preset acrobat action .sequ file (File Name Stamper specifically) to remove the extension from the file name before it places the stamp?

Actually... I took a few minutes and just added a checkbox to to the dialog to include the file extension... or not. The default is checked to keep it consistent with the original. You can grab it at the URL below until I find a more permanent home for it.

http://practicalpdf.com/downloads/FileNameStamper_2.sequ

It'll be simple but not trivial. The Action uses a dialog that you need to be careful not to mess up.

The first thing to know is that .sequ files are just XML. You can open it up in any XML editor and locate the "item" with the name "ScriptCode". This is an encoded version of the JavaScript you need to modify. Just decode it, edit it to remove the file extension, encode it again nd put it back exactly where you found it.

There's a great tool for encoding and decoding the JavaScript here Encode/Decode HTML Entities - Webatic

Shouldn't be too difficult to do, but can you post the code from the Action?