Generating multiple instruction documents with similar content?

Each product we make has a [I]slightly[/I] different process (different part numbers, skipped steps, etc.), but the majority of the instructions are the same. Currently, we maintain separate PowerPoint files for every product's manufacturing process, so when the general process is updated, we have to update [I]every[/I] document individually.

Does anyone know of a more efficient way to deal with this? Ideally, some way to edit and manage information in a centralized location and have it generate/propagate to multiple "child documents"?

All suggestions are welcome. Thank you.

I'm not a Powerpoint expert but I would think that if Word allows you to create form letters in which data like names, addresses, etc. are extracted from a database, then Powerpoint might allow the same thing.

Actually, when I think of creating written documents, I do not think of Powerpoint. That does seem like a misuse of its intended purpose - visual slides for a presentation. I would think some other software, designed for the purpose of creating written documents, would be more appropriate.