title: Are all PDF files compressed?
body: <p>So there are some threads here on PDF compression saying that there is some, but not a lot of, gain in compressing PDFs as PDFs are already compressed.  </p>
  
  <p>My question is: Is this true for all PDFs including older version of the format?</p>
  
  <p>Also I'm sure its possible for someone (an idiot maybe) to place bitmaps into the PDF rather than JPEG etc.  Our company has a lot of PDFs in its DBs (some older formats maybe).  We are considering using gzip to compress during transmission but don't know if its worth the hassle</p>