MOSS Workflows are great for Document Management process. There are many OOTB DMS templates in MOSS and you could leverage those activities with SharePoint Designer. I had a customer that wanted a process that used the Docx file format for authoring/approving the document and convert it to PDF file format before sending outside of the organization. My first idea was to use the Office 2007 capabilities in converting Word to PDF. You can do it easily in the Save As dialog so coding this shouldn't be a problem.
However, this will require installing Office client on the MOSS Server and this is not supported and not recommended. In my early 2003 days, I've tried to use the Word Spell Checker in ASP.Net Server and found it to be a very bad performance idea (and don't forget the many ghost WinWord.exe processes that you find in the task manager's memory) that was quickly replaced with a 3rd party solution.
So nothing in life is free – but what about licensed solutions. I would recommend checking out ActivePDF tools. ActivePDF is the leading provider of PDF generation, conversion and development tools and they provide many tools and SDK for server Word to PDF conversion. You could easily wrap the conversion process (which is very easy once you have the SDK) inside a WF Activity and allow reusing it in many places around your Document Management System.
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