PowerTools for Open XML now contains a new class, OpenXmlRegex, which enables you to search and replace in DOCX and PPTX using regular expressions. Further, this class supports revision tracking - it works properly if you are searching in a document that contains existing revision tracking, and it optionally enables you to introduce new revision tracking markup when replacing text. This task is a little more complicated than it might seem because text can be split into multiple runs, and as appropriate we want the code to match text that spans runs.
In the screen-cast Search and Replace Content in DOCX, PPTX using Regular Expressions, I demonstrate the class, explain the API of the class, and discuss some of the more interesting aspects of introduction of revision tracking markup.
In the screen-cast How the OpenXmlRegex Class Works, I discuss the algorithm that the class uses. This will be interesting to students of Open XML and document formats.