DRM is not to prevent other files from being readable on the Kindle.
DRM refers to the fact that you can't view Amazon Kindle books on other devices (including your computer), or on other Kindles - i.e. no sharing, the purpose of DRM.
How do you load other eBooks onto the Kindle? Just add Amazon DRM.
Granted the PDF converter seems to have some trouble with graphics PDF's, but for books the converter works very well.
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