title_body: How to change the font(s) used on a pdf, or improve how they are rendered? I have an eBook (received from a university where I studied a couple of years back) that has a rather thin font. The text looks as shown in below image.
  
  
  
  This eBook was not published by the university but it seems to be fully editable, meaning that there is no security restrictions on this book and the pages are not images.
  
  The question I wanted to ask:
  
  Is there a way for me to change the fonts to something else, or to improve how they are rendered, in this particular PDF, using either the full version of Adobe Acrobat or some other tool?
  
  (Please note that this font issue is only with this particular PDF and for that reason I am looking for a solution that would not require making a global setting change in Adobe Acrobat.)
upvoted_answer: Based on the sample you provided, you will not be able to change the font on that particular document.  Here is why:
  
  As one commenter already suggested, it is very clear from the sample you provided that the text you are reading is a scanned image of the page and not text being rendered in realtime from a font. I work with scanned documents and OCR tools on a daily basis, so I can say this with confidence. 
  
  
  Look carefully at different occurrences of each letter glyph, and you will notice that they are not identical. Computer fonts do not have inconsistencies between multiple instances of the same glyph, but printed books do.
  The letters in the sample image have the appearance of ink-bleed (which indicates that they were printed on paper) and the typical washed-out look of text which has been run through an image processor to remove the paper grain (this is what causes the "thinness" which is bothering you). 
  Some lines of text have visual distortion from the scanning and dewarping process (look at the text "PAY_TYPE field" for a good example). 
  
  
  All of these things are clear visual indicators of a scanned image.
  
  You are able to select text in the document because there is a hidden OCR text layer "behind" the image which contains the plain text of the book and a mapping file which tells your PDF viewer where each letter is located in the image. There are a few different ways this can be accomplished, but as an example here is a tutorial that shows how to OCR images with Adobe Acrobat (the full software, not Reader).