epubkey.der and DRM removal

[drbmn]

Hi! I have a decrypted pdf (from ebrary) and on the output directory I have 2 archives: The pdf decrypted one and "epubkey.der".

I have read about scripts for using this archive, but the thing is, when i change the directory of my decrypted pdf everything runs fine, so I was wondering what is this archive for or if i can delete it.

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Other thing, is better to use the calibre extension than this solution? In terms of quality (it is strange because the pdf only has 3mb).

Thanks in advance!