My suggestion is

1.       Create a custom content type at site level that allow users to upload documents. This content type  can be attached to any document  library in your sharepoint site.

Note : I am not sure about how to restricting it to  allow only word documents, you may have to workout on this as it is more related to MOSS

2.       You can create K2 workflow using VS2005 which can be attched to a custom content type in shraepoint site  (nder process wizards, use sharepoint workflow Integration à A Sharepoint Content type).

Thank you so much. 

I'm gonna try this. 

Hi zineb,

I'm not sure which version of K2 are you using but on my 4.6 Blackpearl environment you can either make use of the SharePoint Events Process integration or SharePoint Workflow Integration. It depends what your needs are regarding your scenario.

Kind regards,