DRM is not to prevent other files from being readable on the Kindle.
Granted the PDF converter seems to have some trouble with graphics PDF's, but for books the converter works very well.
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.
The Kindle is already able to read more than just Amazon DRMed content, it can handle a number of formats.
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