title_body: How to create DjVu format with selectable text?
upvoted_answer: DjVu files are normally image only. From these file sections can be selected as images but not as text¹.
  
  If OCR was applied during, or after, the conversion to DjVu. Extra information is stored in the files that associate image areas with text. Only if that was done you can select text from such a file².
  
  Applying OCR to a DjVu file can be done online. If you don't like that you could try this script, that uses Tesseract. Or you can go for commercial software such as Document Express.
  
  ¹  e.g. using  the djview program.
  ² In theory one could do OCR on the fly in the DjVu viewer, but I don't think any of the currently available viewers can do that.