title_body: Zoom problem in Kindle with .MOBI converted from PDF I have a Kindle Touch (Kindle (7th Generation)). I have converted a PDF into .MOBI format using PDF converter tools, such as kdpdfopt with all these options set: -mode fp -n- -c -ocr t -h 6.7in -w 4.7in. And then, for smooth rendering, I converted this PDF into .MOBI using Calibre.
  
  Now when I transferred this converted .MOBI file onto my Kindle, the font size remained the same. Even if I try to zoom in, the font size remains constant.
  
  P.S. The font size is set very small which makes reading very poor.
upvoted_answer: It's likely that the CSS created by one of your conversion programs is generating a font-size attribute that is set absolutely (ie in pixels or points) rather than relatively (ie in ems or percents). Without knowing the details of the tools that you're using, it's unlikely we can give much concrete advice. However, if you can get it into Calibre you can probably produce an epub file, and once you have an epub file you should be able to change the CSS, either through Calibre or manually. Once the epub file is formatted to your liking you can use KindleGen (or Calibre, though I would advise KindleGen instead) to create a mobi file for use on your Kindle Touch.