How to convert Word and Excel documents to PDF programmatically?

Office 2007 allows for this. I have found PDFCreator to be good, the VBA is included in sample files, and have heard that CutePDF is also good. PDFCreator and CutePDF are free.

To work without Office, you would need viewers, as far as I know: http://www.microsoft.com/downloads/details.aspx?FamilyID=c8378bf4-996c-4569-b547-75edbd03aaf0&displaylang=EN

http://www.microsoft.com/downloads/details.aspx?familyid=95E24C87-8732-48D5-8689-AB826E7B8FDF&displaylang=en

I needed to do this myself, but managed to get it done with .Net and without 3rd party tools:

MSDN: Saving Word 2007 Documents to PDF and XPS Formats

Pretty simple, about 50 lines of code. However I think you will need Word 2007 installed on the machine as well as the ability to Save As PDF

To convert Word documents to PDF, take a look at jWordConvert, a java library that can do exactly that. This will not work with the Excel files though, only with the Word files. The language is not Sharp, it's Java but you could switch to use IText (which is java) instead of ITextSharp.