pdfWord allows you to transform your Microsoft Word documents into pdf formatted ones for free and without adding advertisement. The sole limitation is related to the size of the Word document to transform; for performance reasons, only the documents with a size lower than 500 Ko will be processed, if you have to work with bigger documents, divide your files in smaller ones.
OK, so you want to stamp your document. Maybe you need to give reviewers some advice about the document's status or sensitivity. This tip from author Ted Padova demonstrates how to add stamps with the Stamp Tool along with related comments.