title_body: How to set a cover image on a PDF on Kindle PW2? How do I set a custom cover image on a PDF downloaded on Kindle PaperWhite 2?
  
  PS1: I use Calibre to convert books and set covers, but it does not help with PDFs. The reason might be that PDF's are considered documents (rather than books) by Kindle PW2. 
  
  PS2: A possible answer would be to convert the PDF to mobi/azw3 format and then set the cover, which I believe will work fine if it wasn't for the bad quality and unreadability of the produced files. Calibre doesn't handle conversion from and to PDF format very well, which is absolutely normal.
upvoted_answer: I've found a similar question to mine, but titled more generally:
  
  Kindle doesn&#39;t show cover