First of all I am assuming that you mean TIFF file. If this is true then removing the association between the TIFF and the application in your browser/explorer should be enough.
My guess is that this is a windows issue and not an Alfresco issue.
one of our clients also need these solution, so we develop the module call Universal Viewer, which could control and decrypt the document such as word, excel, pdf, tif, image, VDO, voice file.
the architecture are
all the document need to encrypt before send to the web users, and the Universal viewer will decrypt it in the temp folder or in the memory. It could also control the Save and print in this Universal Viewer module.
the thing we are concerned right now are the Universal viewer need to install at the first time. Actually, we need the do as the Active X or Flash plugin, but not in that stage. please kindly see the demo in