I'm a huge fan of MPDF it's an incredibly easy HTML to PDF library.

Recently I had some dynamically generated PDF's that would load indefinitely and eventually crash the browser, strange that the same script produced hundreds of PDF's before without any problems, after a lot of debugging I found the root cause, one of the rows coming from a database was quite long in a table cel causing the page to hang.

If I limited the number of characters then the PDf generated just fine, with a lot of trial and error I was at a loss to the solution I didn't fancy digging into the library so I decided to try the latest version in case the issue had already been resolved.

I was using quote an old version of MPDF I upgraded to 5.7 ran the script again and volla! worked first time.

If you experience a similar issue ensure your using the most recent version. Their Forum is a great source of information too.