What is dompdf? Well basically its a HTML to PDF converter. It's rendering engine is built in PHP and is style-driven which means it will download and read external stylesheets, inline style tags, and the style attributes of individual HTML elements.
I won't go into detail of how to use it (unless you want me to or would like to write about it), but recently I had an issue with images not rendering in the pdf. At first I thought it was a permissions problem, then I thought it was an image type problem. It turns out it was a file location issue.
instead of the file location being:
<img src="images/myimage.jpg" style="width:200px;height:200px">
It should be:
<img src="/var/www/images/myimage.jpg" style="width:200px;height:200px">
So as you can see it needs to reference the file from the server side file directory and not just from within the web directory.
Wish someone wrote this, when I needed it....