Other answers explain how to remove the password in the special case of a docx file. IMHO, it is not enough to answer the underlying question: what does that document contains, because even after the password has been removed, you still have to open the document to read it.
Anyway, malicious Word document can be understood in at least 2 ways:
- a word document containing malicious macros
- a specially crafted file targetting a vulnerability in one version of Microsoft Word.
First acception will lead to a rather simple way: just configure word to not process any macro and then open the file.
In second acception, it will really depend on the actual format, but the general guidance is: open it with something that does not rely on Word code. For example, LibreOffice or Oracle OpenOffice are known to be able to process Microsoft Word formats. As they do not share the same code base, it is unlikely that an exploit targetted at Microsoft Word could affect them - in particular, they are a good alternative for ignoring any macro.
You can also use libraries able to process Word documents, but you should first wonder whether they fully implement the specification from scratch or whether they rely on a COM or .NET interface to a Microsoft engine. Do not even try to use them in the latter case!