It seems to take Prince 30 times longer (or more) to create a PDF with lots of high resolution photos than one that's only text. Is it downloading each photo one at a time? If so, would you consider doing a multi-threaded download of images to reduce the wait?

Yes, it's on the roadmap.

Great. Thanks, Mike. I hadn't seen it there.

I'm seeing this issue as well when generating pdfs with lots of photos or high-res photos. Is this something you already fixed?

Do I have anything to gain by putting prince behind a caching proxy server like squid?

A caching proxy would definitely help if you repeatedly retrieve the same resource, eg. if you have a common logo image used in many different PDF documents.

Images should definitely load in parallel as in a browser. From my perspective, that's a much higher priority than all of these Javascript additions I see on the roadmap.

Pulse Energy

Everyone does have different preferences, but we hope that in time we can satisfy them all.

We have now implemented support for parallel downloads. An updated package is available for Ubuntu 14.04, and we will be building alphas for other platforms shortly.

Prince 10 includes support for parallel downloads, enabled by defaults.