Office documents to PDF

I have seen a couple threads about this, but am not getting very straight answers in my searching. I have a web application that needs to take in doc, docx, xls, xlsx files and convert them into PDF. Right now we have a process that uses the Microsoft.Office.Interop.Word library which opens up the document, prints it to a PS file, then GPL GhostScript converts the PS file into a PDF.

Temporary file download link with ASP.NET

I’d like to know how I can generate a temporary download address for my file for a limited time. I know that’s not the best practice and probably using HttpHandlers is the way to go according to http://www.devx.com/codemag/Article/34535/1954
But I’m curious to know how I can use urlrewriting to generate a file name using a GUID or some other cryptic naming technique and make it available for a limited time.
I’d appreciate if anyone points me a good article about it.