We struggled for a long time using OpenXML from Microsoft. Finally, when we needed to convert an MS word document into a PDF, we tried Aspose.Words. Its ability to flawlessly create a PDF document from MS Word is what caused us to buy the product. But then we realized that its functionality was far beyond just creating a PDF and so we replaced all of our OpenXML code with Aspose.Words. We get better support (there is so much information available) and it's plain easier to use. Highly recommend it.