We did look into OCR‘ing manuals, however:
- Limited preservation aspect
- It took more time
- You have to deal with typesetting
- You have to check the OCR‘ed text is correct
In the end, we decided it was too much hassle to bother, especially when the end result is something that does not look like the original.
If a scanned manual is 100 MiB then that is what it is. This should be rather rare though, take some of the current releases; Rolling Ronny and BTTF 2 both have manuals that are around or above 70 pages and they are at around 10-12 MiB. Unless your manuals have lots of colourful pictures on every page it will be hard for the size to spiral out of control.