If I am understanding correctly, you want your DJVU (scanned images with hidden OCR) to be turned into a PDF (scanned images only).
There are multiple ways to handle this.
If you aren't afraid of the commandline, you could use ddjvu to go from DJVU -> PDF:
http://djvu.sourceforge.net/doc/index.html
For example, here is one usage of ddjvu off of Stack Exchange:
https://superuser.com/questions/1005.../596167#596167