I have had success with Apache POIs and reading and writing PowerPoint presentations on GAE. It is important to avoid calls in POIs that will call java.awt classes with security restrictions. To read content from a document, java.awt files are avoided, so you should be fine. In order to write content to a document, you must be careful. I use a predefined template and directly customize text and fonts. This avoids java.awt calls. If you try to create a new PPT document using an existing document as a template (as shown in the POI examples), this will fail due to java.awt and GAE calls prohibiting them. Your mileage may vary depending on Word documents, as I assume there are fewer graphic library calls.
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