Processing Microsoft Office 2003 documents

I’m working on a WPF application that provides some simple functions to process Office 2003 (Word, Powerpoint and Excel) documents (these include opening/ viewing the documents, adding comments to the documents and saving back to the correspondent nature extension - eg: .doc, .ppt and .xls). I’m thinking of two approaches, one is to convert everything to images files (jpeg) and display them (in which case I’m not very sure of how to add comment and save back), the second way is to actually try to interact/ manipulate these documents using the office interop lib. Please give me some advice on which approach should I take or suggest a new one. Am I heading for the right direction or going astray? Many thanks to you all in advance.